Cec Diagnosing & Testing Ford Bronco II I

TEST EQUIPMENT

The following equipment is recommended to diagnose and test EEC-IV system. Some equipment is REQUIRED to perform tests. DO NOT attempt to test this system without proper equipment. Damage to vehicle components will result if improper equipment is used.

1. Self-Test Automatic Read-Out (STAR) diagnostic tester is recommended but not required. It is specially built for the EEC-IV system and is used to display, as numerals, the 2- digit service codes that are programmed into the control module.
2. Analog Volt/Ohmmeter (VOM) with 0-20V DC range. This can be used as an alternate to the diagnostic tester.
3. Digital Volt/Ohmmeter (DVOM) with minimum 10 megaohm input impedance.
4. Breakout Box (Part No. 014-00322). This is a jumper wire assembly which connects between the vehicle harness and the ECA. The breakout box is REQUIRED to perform certain tests on the system. Ford Motor Co. specifically states that using the probe from a DVOM will cause PERMANENT DAMAGE to the ECA 60- pin connector. "Test Pin" as called out in «CIRCUIT TESTS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) refers to the pins on the breakout box. Once the breakout box has been installed during a test sequence, it may be left connected for the remainder of the test.
5. Vacuum gauge with 0-30 in. Hg range and resolution (unit on scale) of 1 in. Hg.
6. Tachometer with 0-6000 RPM range, accuracy +/- 40 RPM, and a resolution of 20 RPM.
7. Vacuum pump with 0-30 in. Hg range.
8. Timing light.
9. Spark tester. A modified spark plug with side electrode removed and alligator clip attached may be used.
10. Fuel Injection Pressure Gauge (Part No. T80L-9974-A).
11. Non-powered test lamp.
12. Jumper wire, about 15" long.
13. MAP/BP tester. Unit plugs into MAP/BP sensor circuit and DVOM to check input and output voltages to verify correct sensor operation.

Note. The STAR diagnostic tester is available from Hikok Electrical Instrument Co., 10514 Dupont Ave., Cleveland, OH 44106.

TEST CONNECTOR LOCATIONS

The SELF-TEST connector is found in different locations depending upon model. On Aerostar, the connector can be found on rear of left front fender apron. The Bronco II and Ranger have the connector located on the right front wheelwell, below fuel pump relay. On Bronco and pickups, the connector can be found on the right front wheelwell, below starter relay. Econoline vans have the connector located on right front fender apron, near starter relay.

DIAGNOSTIC PROCEDURE

This diagnostic procedure is used to test and service the EEC-IV system. It is divided into 2 test formats: QUICK TEST , a functional system test, and CIRCUIT TESTS , a number of specific circuit and components tests. To test and service EEC-IV system, perform the QUICK TEST first.

If vehicle passes KEY ON/ENGINE OFF (KOEO) , KEY ON/ENGINE RUNNING (KOER) , and CONTINUOUS SELF-TESTS of QUICK TEST without running any CIRCUIT TESTS , the EEC-IV is okay. Problem exists somewhere else besides the EEC-IV system. If QUICK TEST fails, perform only these tests that are specified by the failed step.

PREPARATION

Correct test results for system are dependent on the correct operation of several related non-EEC components and systems. All non-EEC problems should be corrected before attempting to diagnose the EEC system.

Before hooking up any equipment to diagnose the EEC system, make the following checks

1. Verify condition of air cleaner and air ducting.
2. Check all vacuum hoses for leaks, restrictions, and proper routing.
3. Check the EEC-IV system wiring harness electrical connections for corrosion, loose or detached connectors, loose wires or terminals, and proper routing.
4. Check the ECA, sensors and actuators for physical damage.
5. Perform all necessary safety precautions to prevent personal injury or vehicle damage.
6. Set parking brake and place shift lever in "P" for automatic transmission, or Neutral for manual transmission. DO NOT move shift lever during testing unless specifically directed.
7. Turn off all lights and accessories, and make sure vehicle doors are closed when making readings.
8. Check and correct coolant level.
9. Start engine and idle until upper radiator hose is hot and pressurized and throttle is off fast idle. Check for leaks around exhaust manifold, exhaust gas oxygen sensor, and vacuum hose connections.
10. Turn ignition key off. Service items as required, then go to «EQUIPMENT HOOK-UP»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__equipment-hook-up-scheme-41) .

Note. If engine will not start, starts but stalls, idles rough or runs rough, go through KEY ON/ENGINE OFF SELF-TEST. If any of the above conditions are still present after a code 11 in the KEY ON/ENGINE OFF SELF-TEST, go to TEST A - NO START , step 2) for a no start condition. If engine stalls or runs rough, go to DIAGNOSIS BY SYMPTOM TEST .

Analog Vom

1. Turn ignition key off. Connect jumper wire from Self-Test Input (STI) pigtail to pin No. 2 (Signal Return) on SELF-TEST connector. Set VOM at 0-15V DC range and connect positive lead of VOM to positive battery terminal.
2. Connect negative VOM lead to pin No. 4 self-test output (STO) on SELF-TEST connector. (Scheme 41) Connect timing light, then go to «KEY ON/ENGINE OFF (KOEO) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-off-koeo-self-test).

Note. Diagnostic tester hook-up instructions apply to STAR tester only. If other then STAR tester is being used, follow diagnostic tester manufacturer instructions.

Equipment Hook-Up. Scheme 41

Diagnostic Tester

Turn ignition key off. Connect color coded adapter cable leads to diagnostic tester. Connect adapter cable's 2 service connectors to vehicle's SELF-TEST connectors. Connect timing light, then go to KEY ON/ENGINE OFF (KOEO) SELF-TEST .

Reading Self-Test Codes

Service codes are transmitted to pin No. 4 (Self-Test Output) of SELF-TEST connector in the form of timed pulses. All service codes are 2 digit numbers which are generated one digit at a time. Codes are shown as voltage pulses (needle sweeps) on an analog volt/ohmmeter (VOM).

If a VOM is being used, careful attention to the length of the pauses is necessary in order to read the codes correctly. There will be a 2 second pause between each DIGIT in a code. There will be a 4 second pause between each CODE. The continuous memory codes are separated from the functional test service codes by a 6 second delay, a single 1/2 second sweep, and another 6 second delay.

If a Self-Test Automatic Read-Out (diagnostic) tester is used, it will count the pulses and display them as a digital code. The STAR diagnostic tester will add a zero (0) to single digit (Separator and Dynamic Response) codes. Other diagnostic testers may or may not have this function.

Separator Pulse

A single 1/2 second separator pulse is issued 6-9 seconds after last functional KEY ON/ENGINE OFF SELF-TEST code. Then 6-9 seconds after the single 1/2 second separator pulse, the continuous memory codes will be displayed.

Continuous Memory Codes

These codes are issued as a result of information stored during CONTINUOUS MONITOR (WIGGLE) TEST . These codes are displayed only during KEY ON/ENGINE OFF (KOEO) SELF-TEST and after separator code. These codes should be used to diagnose ONLY when KEY ON/ENGINE OFF and KEY ON/ENGINE RUNNING (KOER) SELF-TEST result in Code 11 and all QUICK TEST steps have been successfully completed.

QUICK TEST

The QUICK TEST diagnostic procedure is a functional test of the EEC-IV system. It consist of 4 basic test steps. These basic steps must be carefully followed in sequence, otherwise misdiagnosis, or replacement of non-faulty components may result.

Perform QUICK TEST as follows: Perform PREPARATION and EQUIPMENT HOOK-UP steps, KEY ON/ENGINE OFF (KOEO) SELF-TEST , TIMING CHECK , KEY ON/ENGINE RUNNING (KOER) SELF-TEST , and CONTINUOUS SELF-TEST . After all tests, servicing, or repairs have been completed, repeat QUICK TEST to ensure EEC-IV system works properly.

1. The «KEY ON/ENGINE OFF (KOEO) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-off-koeo-self-test) is a static check of EEC-IV system inputs and outputs. The «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) verifies the system's ability to compute and maintain a fixed spark timing during SELF-TEST.
2. The «KEY ON/ENGINE RUNNING (KOER) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-running-koer-self-test) is a dynamic system check with the engine under actual operating conditions and at normal operating temperature. The «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) checks the sensor inputs for opens and shorts while the vehicle is in operation.
3. The KOEO and KOER SELF-TESTS are intended to detect faults present at the time of testing, not intermittent faults. Intermittent faults are detected by «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) .

KEY ON/ENGINE OFF (KOEO) SELF-TEST

Note. Continuous memory codes recorded in this step will be used for diagnosis in CONTINUOUS SELF-TEST .

Code Output

Correct test results for system are dependent on the correct operation of several related non-EEC components and systems. It may be necessary to correct faults in these areas before EEC-IV will pass QUICK TEST .

Verify that vehicle has been properly prepared. See PREPARATION and EQUIPMENT HOOK-UP . Turn ignition on to start SELF- TEST. DO NOT depress throttle during test. Observe and record all service codes.

1. If engine does not start, go to «TEST A - NO START»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-a-no-start) , step 2). If KEY ON/ENGINE OFF (KOEO) code and continuous memory indicate a pass (Code 11), go to «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) .
2. If any KOEO code is displayed with continuous memory code 11, KOEO SELF-TEST indicates a fault. Record codes and go to TEST RESULTS & ACTION TO TAKE in this test.
3. If any KOEO or any continuous memory code is displayed, KOEO SELF-TEST and continuous memory indicate a fault. Record codes, but DO NOT repair continuous memory codes at this time. All KOEO and KOER SELF-TEST codes MUST be repaired first. Go to TEST RESULTS & ACTION TO TAKE in this test.
4. If KOEO code 11 displayed with ANY continuous memory code (except 15), continuous memory indicates a fault. Record codes, but DO NOT repair continuous memory codes at this time. KOEO and KOER SELF-TEST codes MUST be repaired first. Go to «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) .
5. If KOEO code 11 is displayed and continuous memory code is 15, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 9). If NO CODES are displayed, repeat SELF-TEST and verify that no service codes are present, then go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 1).

Test Results & Action To Take

1. Perform the test indicated in the «KEY ON ENGINE OFF (KOEO) CIRCUIT TEST MENU»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table for that specific engine. Start with the first code displayed. If the tests refer you to other checks, perform them as instructed.
2. When more than one code is displayed, repair problems in the order that codes are displayed. Whenever a repair is made, repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If NO CODES appear, repeat SELF-TEST to verify that no service codes are present, and then go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 1).

Note. See CIRCUIT TESTS at back of article.

CODE/TEST MENU (KOEO)

KEY ON ENGINE OFF (KOEO) CIRCUIT TEST MENU

TIMING CHECK

Note. If engine will not start, go to TEST A - NO START . If engine starts but stalls while testing, go to DIAGNOSIS BY SYMPTOM TEST.

1. Turn ignition off and wait 10 seconds. Verify that SELF-TEST has been activated. Restart engine and check timing while in SELF-TEST mode. You are allowed 2 minutes to check timing from the time the last code is displayed.
2. Correct SELF-TEST timing equals base ignition timing (10° BTDC on all engines) plus 17-23° BTDC. If timing is not 27-33° BTDC, go to «TEST GG - SPARK TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-gg-spark-timing-check) . If timing is 27-33° BTDC, go to «KEY ON/ENGINE RUNNING (KOER) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-running-koer-self-test) .

KEY ON/ENGINE RUNNING (KOER) SELF-TEST

Note. If engine will not start, go to TEST A - NO START . If engine starts but stalls while testing, go to DIAGNOSIS BY SYMPTOM TEST.

1. Deactivate SELF-TEST (disconnect jumper wire). Start and run engine at 2000 RPM for 2 minutes to warm up EGO sensor. Turn engine off and wait 10 seconds. Insert jumper to activate SELF-TEST. DO NOT depress throttle during test unless a Dynamic Response code occurs.
2. Start engine. The engine ID code will be displayed. On 2.3L, 2.9L and 3.0L engine equipped vehicles, depress and release brake pedal, ONE TIME ONLY, after engine ID code has been displayed. This will test the Brake On/Off (BOO) switch. On pickups equipped with 4.9L and 5.0L engines, steering wheel must be turned 1/2 turn and released after ID code.
3. Run test. If Dynamic Response code 1 (10 with STAR tester) occurs, briefly accelerate engine to wide open throttle (WOT). The ENGINE RUNNING SELF-TEST service codes will then be displayed. Observe and record all codes.

Note. The Engine ID code is 1/2 the number of cylinders (a 2 equals a 4 cylinder engine). Diagnostic tester adds a zero to all single digit readings. A "20" on Diagnostic tester equals a 4 cylinder engine. Some vehicles do not require a brief WOT, they will not display a 1 (10).

1. If NO CODES appear, repeat SELF-TEST and verify that no service codes are present, and then go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 1). If engine ID code is 2, 3 or 4 (20, 30 or 40 with STAR tester), and code 11 is displayed, ENGINE RUNNING SELF-TEST portion is okay. If symptom was of an intermittent nature, go to «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) . If symptom is present, go to «DIAGNOSIS BY SYMPTOM TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__diagnosis-by-symptom-test) . Otherwise «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) is complete, and EEC-IV system is okay.
2. If Engine ID code is 2, 3 or 4 (20, 30 or 40 with STAR tester), and any code other than 11 appears, ENGINE RUNNING SELF-TEST portion is at fault. Perform the test indicated in the «KEY ON/ENGINE RUNNING CIRCUIT TEST MENU»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table for that specific engine.
3. Start with the first code displayed. If the tests refer you to other checks, perform them as instructed. When more than one code is displayed, repair problems in the order that codes are displayed. Whenever a repair is made repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

CODE/TEST MENU (KOER)

KEY ON/ENGINE RUNNING CIRCUIT TEST MENU

CONTINUOUS SELF-TEST

Note. CONTINUOUS SELF-TEST is subdivided into 4 steps: CONTINUOUS MEMORY CODES, CLEARING CONTINUOUS MEMORY CODES, CONTINUOUS MEMORY CODES TO BE TESTED, and TEST RESULTS & ACTION TO TAKE. Perform steps in sequence.

1. To ensure proper diagnosis of continuous memory codes, «PREPARATION»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__preparation) , «EQUIPMENT HOOK-UP»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__equipment-hook-up-scheme-41) , «KEY ON/ENGINE OFF (KOEO) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-off-koeo-self-test) , «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) , and «KEY ON/ENGINE RUNNING (KOER) SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-running-koer-self-test) must be successfully completed. If both KEY ON/ENGINE OFF and ENGINE RUNNING SELF-TEST display code 11 (Pass), go to CLEARING CONTINUOUS MEMORY CODES.
2. If not, return to «PREPARATION»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__preparation) step and make the necessary repairs indicated in KEY ON/ENGINE OFF and ENGINE RUNNING SELF-TEST before going to CLEARING CONTINUOUS MEMORY CODES.

Clearing Continuous Memory Codes

1. Perform KEY ON/ENGINE OFF SELF-TEST. When the first service code appears, exit SELF-TEST program by disconnecting STAR tester or by removing jumper wire from Self-Test Input (STI) pigtail. Exiting «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) in this manner will clear all codes stored in continuous memory.
2. Repeat KEY ON/ENGINE OFF SELF-TEST. If code output is 11-10-11, go to CONTINUOUS MEMORY CODES TO BE TESTED. If code output is not correct, check Self-Test Input (STI) circuit for short to ground. Repair short and repeat CLEARING CONTINUOUS MEMORY CODES step.

Continuous Memory Codes To Be Tested

Check list of Continuous Memory codes that were recorded in KEY ON/ENGINE OFF and ENGINE RUNNING SELF-TESTS. Disregard any codes that have already been repaired. To confirm remaining codes, go to TEST RESULTS & ACTION TO TAKE.

1. Ensure that all previous «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) steps have been successfully completed. Verify proper test equipment hook-up. See «EQUIPMENT HOOK-UP»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__equipment-hook-up-scheme-41) in this article. Make sure that SELF-TEST is deactivated. DO NOT activate SELF-TEST unless specifically instructed to do so.
2. Using service codes obtained in CONTINUOUS MEMORY CODES TO BE TESTED, perform the test(s) indicated in the «CONTINUOUS SELF-TEST CIRCUIT TEST MENU»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table for that specific engine. While performing «CIRCUIT TESTS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , one or both of the «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) may have to be used to find intermittent fault.

CONTINUOUS MONITOR (WIGGLE) TEST

The Self-Test Output (STO) will be activated each time a fault is detected. If the STO is activated long enough during the wiggle tests a service code will be stored. A fault is indicated by a 10.5 volt or greater deflection on VOM. STAR tester LED turns off.

1. «KEY ON/ENGINE OFF»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-off-koeo-self-test) Test: With SELF-TEST deactivated, turn ignition on to enter into wiggle mode.
2. «KEY ON/ENGINE RUNNING»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__key-onengine-running-koer-self-test) Test: Activate SELF-TEST and perform ENGINE RUNNING SELF-TEST. After service code output has finished, do not turn engine off or deactivate SELF-TEST. About 2 minutes after code 11 has been displayed, wiggle mode will start. The system will remain in wiggle mode until SELF -TEST is deactivated or engine is turned off.

Note. An alternate method of entering CONTINUOUS MONITOR (WIGGLE) TEST with engine running is to start ENGINE RUNNING SELF- TEST, exit, and re-enter ENGINE RUNNING SELF-TEST without turning engine off.

1. Observe VOM while moving, wiggling, and tapping the system harness (in short sections), connectors, and sensors. If an intermittent condition is created, the monitor will indicate this by storing a service code. Carefully inspect harness and associated connectors of affected circuits.
2. If an intermittent condition is not created, carefully disconnect sensor from harness. Remove terminals from connector and visually inspect terminals at both ends for corrosion, bad crimps, improperly seated terminals, etc.
3. Reconnect harness after inspection. Disconnect ECA from harness as carefully as possible. Remove and inspect terminals associated with sensor being checked.
4. If an intermittent condition cannot be created, reconnect connector and erase the «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) service codes. To erase service codes, activate KEY ON/ENGINE OFF SELF-TEST.
5. Remove jumper from Self-Test Input (STI) terminal as soon as first service code appears. Repeat SELF-TEST with jumper to verify that service codes have been erased. «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) is complete.

CODE/TEST MENU (CONTINUOUS)

CONTINUOUS SELF-TEST CIRCUIT TEST MENU

Dynamic Response Check

The Dynamic Response Check verifies movement of the TPS and MAP sensors during wide open throttle (WOT) as part of the ENGINE RUNNING SELF-TEST. The signal to perform WOT is a single pulse (1) when using a VOM or code 10 on STAR tester. Briefly accelerate engine to WOT for one second.

Output State Check

The Output State Check is used as an aid in servicing output actuators associated with the EEC-IV system. It allows you to energize and de-energize most of the system output actuators on and off on command.

This mode is entered after all codes have been received from KEY ON/ENGINE OFF and CONTINUOUS SELF-TEST . At this time, leave SELF-TEST activated and depress throttle. Each time throttle is depressed, the output actuators will change state (go from on to off, or off to on).

DIAGNOSIS BY SYMPTOM TEST

The DIAGNOSIS BY SYMPTOM TEST is divided into specific engine sections. Each section will describe testing procedures and codes for that engine. Use appropriate DIAGNOSIS BY SYMPTOM TEST. The CIRCUIT TESTS are common to all engines, unless noted in test procedures.

2.3L EFI

Use this test procedure ONLY when directed to do so by results of QUICK TEST or steps in CIRCUIT TESTS . Follow test procedures carefully.

1. When engine stalls in operation or during SELF-TEST, runs rough or misses, or has an "always rich" or "always lean" condition, perform the following checks: Perform SYSTEM CHECK, ISC Check. Use «TEST II - SYSTEM CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-ii-system-check) , step 1). Check MAP sensor, using «TEST G - MAP/BP SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-g-mapbp-sensor) , step 11). Check ISC (By-Pass Air), using «TEST X - IDLE SPEED CONTROL (BY-PASS AIR)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-x-idle-speed-control) , step 1). Check for, and repair, any bad ground or power connections. Check ignition components (cap, rotor, wires, coil, & plugs). Check basic engine components (valves, cam timing, compression, etc.).
2. When detonation (spark knock) occurs, go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , step 1).
3. If no fast idle occurs when A/C is turned on, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
4. If shift indicator light is always on or off, go to «TEST BB - SHIFT INDICATOR LIGHT (SIL)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-bb-shift-indicator-light) , step 1).
5. If A/C does not cut off under wide open throttle conditions, go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
6. If engine surges at idle with A/C on, go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 8).
7. If engine stumbles after hot restart (check HEGO), go to «TEST R - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-r-23l-efi-fuel) .3L EFI FUEL CONTROL, step 1).
8. If engine stalls while parking vehicle, go to «TEST P - POWER STEERING PRESSURE SWITCH (PSPS)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-p-power-steering-pressure) , step 3).
9. If A/C compressor runs continuously, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 4).
10. If fuel pump runs with key off, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 12).

2.9L EFI

Use this test procedure ONLY when directed to do so by results of QUICK TEST or steps in CIRCUIT TESTS . Follow test procedure carefully.

1. When engine stalls in operation or during SELF-TEST, runs rough, or misses, perform the following checks: Perform SYSTEM CHECK, ISC Check. Use «TEST II - SYSTEM CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-ii-system-check) , step 1). Check MAP sensor, using «TEST G - MAP/BP SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-g-mapbp-sensor) , step 11). Check for, and repair, any bad ground or power connections. Check ignition components (cap, rotor, wires, coil, & plugs). Check basic engine components (valves, cam timing, compression, etc.).
2. If detonation (engine knock) occurs, go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , step 1).
3. If no fast idle occurs when A/C is turned on, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
4. If A/C does not cut-off during wide open throttle (WOT), go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
5. If engine stumbles after hot restart (check HEGO), go to «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 15).
6. If engine stalls while parking vehicle, go to «TEST P - POWER STEERING PRESSURE SWITCH (PSPS)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-p-power-steering-pressure) , step 3).
7. If fuel pump runs with key off, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 12).

3.0L EFI

Use this test procedure ONLY when directed to do so by results of QUICK TEST or steps in CIRCUIT TESTS . Follow test procedure carefully.

1. When engine stalls in operation or during SELF-TEST, runs rough, or misses, perform the following checks: Perform SYSTEM CHECK, ISC Check. Use «TEST II - SYSTEM CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-ii-system-check) , step 1). Check MAP sensor, using «TEST G - MAP/BP SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-g-mapbp-sensor) , step 11). Check for, and repair, any bad ground or power connections. Check ignition components (cap, rotor, wires, coil, & plugs). Check basic engine components (valves, cam timing, compression, etc.).
2. If detonation (engine knock) occurs, go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , step 1).
3. If no fast idle occurs when A/C is turned on, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
4. If shift indicator light is always on or off, go to «TEST BB - SHIFT INDICATOR LIGHT (SIL)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-bb-shift-indicator-light) , step 1).
5. If A/C does not cut-off during wide open throttle (WOT), go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
6. If engine stumbles after hot restart (check HEGO), go to «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 15).
7. If engine stalls while parking vehicle, go to «TEST P - POWER STEERING PRESSURE SWITCH (PSPS)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-p-power-steering-pressure) , step 3).
8. If engine has poor idle, rolling idle, harsh shift and/or poor fuel economy, go to «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) , step 27).
9. If fuel pump runs with key off, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 12).

4.9L EFI

Use this test procedure ONLY when directed to do so by results of QUICK TEST or steps in CIRCUIT TESTS . Follow test procedure carefully.

1. When engine stalls in operation, runs rough, misfires, or lacks power perform the following checks: Check for, and repair, any bad ground or power connections. Check ignition components (cap, rotor, wires, coil and plugs). Check basic engine components (valves, cam timing, compression, etc.). Check fuel delivery. Check EGR valve for correct function.
2. If detonation (engine knock) occurs and/or engine idles roughly, check EGR valve for correct function, then go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , step 1).
3. If engine lacks fast idle with A/C on, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
4. If shift indicator light is always on or off, go to «TEST BB - SHIFT INDICATOR LIGHT (SIL)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-bb-shift-indicator-light) , step 1).
5. If engine stumbles after a hot re-start, go to «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 20).
6. If fuel pump runs with key off, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 12).

5.0L EFI

Use this test procedure ONLY when directed to do so by results of QUICK TEST or steps in CIRCUIT TESTS . Follow test procedure carefully.

1. When engine stalls in operation or during SELF-TEST, runs rough, or misses, perform the following checks: Perform SYSTEM CHECK, ISC Check. Use «TEST II - SYSTEM CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-ii-system-check) , step 1). Check MAP sensor, using «TEST G - MAP/BP SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-g-mapbp-sensor) , step 11). Check ISC By-Pass Air, using «TEST X - IDLE SPEED CONTROL (BY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-x-idle-speed-control) -PASS AIR), step 1). Check for, and repair, any bad ground or power connections. Check ignition components (cap, rotor, wires, coil and plugs). Check basic engine components (valves, cam timing, compression, etc.).
2. If detonation (engine knock) occurs, go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , step 1).
3. If no fast idle occurs when A/C is turned on, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
4. If shift indicator light is always on or off, go to «TEST BB - SHIFT INDICATOR LIGHT (SIL)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-bb-shift-indicator-light) , step 1).
5. If A/C does not cut-off during wide open throttle (WOT), go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 1).
6. If engine surges at idle with A/C on, go to «TEST CC - WIDE OPEN THROTTLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 8).
7. If engine stumbles after hot restart (check HEGO), go to «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 15).
8. If engine stalls while parking vehicle, go to «TEST P - POWER STEERING PRESSURE SWITCH (PSPS)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-p-power-steering-pressure) , step 3).
9. If fuel pump runs with key off, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 12).

HOW TO USE CIRCUIT TESTS

1. DO NOT perform any CIRCUIT TEST unless told to do so by «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . Make sure all non-EEC related faults are corrected. DO NOT replace any part unless directed to do so. When more than one service code is received, start with the first code displayed. NOTE: Procedures in the TESTING section of this article are not in absolute numerical order. Procedures not related to this engine have been removed to eliminate confusion.
2. DO NOT measure voltage or resistance at ECA or connect any test lamps to it, unless specified. All measurements are made by probing the REAR of the connector. Isolate both ends of a circuit and turn key off whenever checking for shorts or continuity, unless specified.
3. Disconnect solenoids and switches from harness before measuring continuity, resistance, or applying 12 volts. Follow each test step in order until fault is found. After each repair, check all component connections and repeat CIRCUIT TEST(S).
4. An "open" is defined as any resistance reading higher than 5 ohms, unless specified in «CIRCUIT TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) . A "short" is defined as any resistance reading less than 10,000 ohms to ground, unless specified in «CIRCUIT TESTS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) .
5. On «CIRCUIT TESTS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) be aware that the following non-EEC related areas may also be at fault. These include: ignition coil, distributor cap and rotor, spark plug wires, fouled spark plugs, EGR valve and gasket, air filter, poor power and ground circuits, fuel pressure, intake and exhaust manifold leaks, engine not at normal operating temperature, and problems with PCV valves or fuel contaminated engine oil.

Note. Fuel contaminated engine oil may affect some service codes. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST . If problem is corrected, change engine oil and filter.

TEST A - NO START

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel quantity and quality, ignition system damage, cracks, moisture, etc., engine mechanical conditions such as valves, timing belt, etc. Also included are starter and battery circuit problems.

1. Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, but does not start or else stalls after starting, go to next step.
2. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage at TPS harness connector between voltage reference (VREF) and signal return. If reading is less than 4.0 volts or higher than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) . If reading is between 4.0 and 6.0 volts, reconnect TPS and go to next step.
3. Disconnect any spark plug wire and connect spark tester between plug wire and engine ground. Crank engine and check for spark. If spark exists, connect spark plug wire and go to Step 13). If no spark, connect spark plug wire and go to next step.
4. Remove high tension coil wire from distributor and install spark tester. Check for spark while cranking engine. If spark exists, connect coil wire and service or repair TFI ignition system. If there is no spark, connect coil wire and go to next step.
5. Turn key off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and disconnect TFI. Measure resistance between test pin 16 and TFI harness connector ignition ground. If reading is more than 5 ohms, repair harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
6. With breakout box installed and box timing switch on "Distributor" position, connect TFI and ECA. Try to start vehicle. If vehicle starts, go to Step 10). If vehicle does not start, go to next step.
7. Move breakout box timing switch to "Computed" position. Set DVOM on 20-volt scale and measure voltage between test pin 36 and chassis ground while cranking engine. If reading is between 3.0 and 6.0 volts, EEC-IV system is NOT at fault. Diagnose TFI ignition system. If reading is less than 3.0 volts or more than 6.0 volts, go to next step.
8. Turn key off and wait 10 seconds. With breakout box installed, disconnect ECA and TFI. Set DVOM on 200,000-ohm scale and measure resistance between test pin 36 and test pins 16, 20, 26, 40, and 60 for short to ground. Measure resistance between test pin 36 and test pins 37 and 57 for short to power. Measure resistance between test pins 36 and 56 for short to PIP. If any reading is less than 10,000 ohms, repair short in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If engine still does not start, go to next step. If all readings are 10,000 ohms or higher, go to next step.
9. Turn key off and wait 10 seconds. With breakout box installed, connect ECA, but leave TFI disconnected. Set DVOM on 200 ohm scale. Measure resistance between test pin 36 and test pins 37 and 57 for short to power. Measure resistance between test pin 36 and test pins 40 and 60 for short to ground. If any reading is less than 5 ohms, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 5 ohms or higher, connect TFI and go to next step.
10. With breakout box installed and DVOM on 20-volt scale, measure voltage between test pin 56 and 16, while cranking engine. If reading is between 3.0 and 6.0 volts, remove breakout box. Replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 3.0 volts or more than 6.0 volts, go to next step.
11. Install breakout box, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect TFI and ECA. Measure resistance between test pin 56 and TFI connector PIP circuit. If reading is 5 ohms or more, repair open PIP circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings is less than 5 ohms, go to next step.
12. With breakout box installed and ECA disconnected, turn key off. Disconnect TFI connector and set DVOM on 200,000-ohm scale. Measure resistance between test pin 56 and test pins 16, 20, 26, 40, and 60 for short to ground. Measure resistance between test pin 56 and test pins 37 and 57 for short to power. Measure resistance between test pin 56 and test pin 36 for short to Spark Output (SPOUT). If any reading is less than 10,000 ohms, repair PIP circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are higher than 10,000 ohms, diagnose TFI ignition system.
13. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damaged, loose, or corroded pins or wires. Repair wiring as necessary. Install breakout box and connect ECA. Make sure that box timing switch is in "Computed" position. Set DVOM on 20 volt scale and measure voltage between test pin 36 and chassis ground while cranking engine. If reading is between 3.0 and 6.0 volts on fuel injected engines, go to next step. If reading is less than 3.0 volts or more than 6.0 volts on all engines, go to step 10).
14. Disconnect all electrical connections at injectors. Connect pressure gauge to fuel diagnostic valve (if equipped) on fuel rail. Note initial pressure reading. Pressurize fuel system by turning key on for 1 second, turning key off, and then waiting 10 seconds. Repeat on, off, and wait sequence 5 times. Turn key off and wait 10 seconds. Connect all injectors. If pressure increased, go to «TEST II - SYSTEM CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-ii-system-check) , step 1) for EFI fuel injected engines. If pressure did not increase, go to next step.
15. With key off and fuel pressure gauge installed, locate fuel pump inertia switch and push button on switch to reset it. If switch will not reset to on, replace inertia switch and repeat step 14). If switch button was already on, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 1). Observe pressure gauge as system is pressurized as in step 14). If pressure reading increases, repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If pressure reading does not increase, go to «TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-t-fuel-pump-circuit) , step 1).

TFI Module Circuits. Scheme 42

TEST B - VEHICLE BATTERY

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: battery cables and ground straps, voltage regulator and alternator, and ignition switch.

1. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage across battery terminals. If reading is less than 10.5 volts, service or replace discharged battery. If reading is 10.5 volts or higher, go to next step.
2. Turn key off, wait 10 seconds. With breakout box installed and ECA connected, set DVOM on 200-ohm scale and measure resistance between test pins No. 40 and 60 and negative battery post. If reading is less than 0.5 ohms, go to next step. If reading is 0.5 ohms or higher, correct cause of resistance between negative side and pins No. 40 or 60. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
3. With breakout box installed and ECA connected, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pins No. 46, 40 and 60. If either reading is 0.5 ohms or less, go to step 4). If resistance is more than 0.5 ohms, disconnect ECA and inspect for corrosion or damage. Repair and recheck resistance. If reading is still too high, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
4. With breakout box installed and ECA connected, turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between test pin 46 and test pins 40 and 60. If reading is 5 ohms or less, go to step 5). If reading is more than 5 ohms, correct cause of resistance in Signal Return harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Turn key on leaving engine off. With ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and Keep Alive Power (KAPWR) circuit (test pin No. 1) at EEC power relay. If reading is less than 10.5 volts, check KAPWR and vehicle power (V Power) circuits for shorts to ground. Also check KAPWR circuit from EEC power relay to battery positive post for open circuit. If reading is 10.5 volts or higher, go to next step.
6. Turn key on, leaving engine off. With ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and ignition circuit at EEC power relay. If reading is less than 10.5 volts, check for open ignition switch circuits. Repair wiring and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or higher, go to next step.
7. Turn key off, wait 10 seconds. With ECA connected, set DVOM on 200-ohm scale. Measure resistance between battery negative post and ground circuit at EEC power relay. If reading is 0.5 ohms or less, go to next step. If reading is higher, repair open circuit or short to ground in ground circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
8. Turn key on, leaving engine off. With ECA connected, set DVOM on 20-volt scale. Measure voltage between battery negative post and vehicle power circuit at EEC power relay. If reading is less than 10.5 volts, replace EEC power relay and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volt or higher, repair open vehicle power circuit. If okay, repair short to ground in vehicle power relay circuit.
9. Turn key on, leaving engine off. Connect VOM or STAR tester to SELF-TEST connector. With SELF-TEST deactivated, enter into «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) . Observe VOM or STAR tester LED for indication of fault while bending and twisting harness from EEC power relay to ECA. If code 72 or 78 is displayed or if fault is indicated, isolate fault in vehicle power circuit, and repair as necessary. If code 72 or 78 is not displayed or if fault is not indicated, inspect EEC power relay and connectors for damaged pins, corrosion, etc. If okay, replace EEC power relay and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Battery Circuits. Scheme 43

TEST C - REFERENCE VOLTAGE

1. Install breakout box, leaving ECA connected. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin 37 and signal return in SELF-TEST connector. If reading is less than 10.5 volts, go to «TEST B - VEHICLE BATTERY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-b-vehicle-battery) , step 1). If reading is 10.5 volts or higher, go to next step.
2. With breakout box installed and ECA connected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pins 26 and 46. If reading is 6.0 volts or higher, go to step 4). If reading is 4.0 volts or lower, go to step 5). If reading is between 4.0 and 6.0 volts, go to next step.
3. With breakout box installed and ECA disconnected, turn key off. Set DVOM on 200-ohm scale. Measure resistance from test pins 26 and 46 to suspect VREF sensor harness connector. If all readings are less than 5 ohms, connect sensors. If VREF circuit is okay, repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If any reading is 5 ohms or higher, repair open circuit in VREF or signal return and then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
4. Turn key off and wait 10 seconds. With breakout box installed and ECA disconnected, turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin 26 and battery ground. If reading is less than 0.5 volts, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 0.5 volts or higher, repair short to battery power in EEC-IV harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . Replace ECA if fault still occurs.
5. Shorted TPS Sensor. Turn key off and wait for 10 seconds. With breakout box installed and ECA connected, disconnect Throttle Position Sensor (TPS) from vehicle harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin 26 and 46. If reading is 4.0 volts or higher, replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If less than 4.0 volts on models without EGR Valve Position (EVP) sensor, go to step 7). If reading is less than 4.0 volts on models with EVP sensor, go to next step.
6. Shorted EVP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect EVP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin 26 and 46. If reading is 4.0 volts or higher, replace EVP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 4.0 volts, go to next step.
7. Shorted MAP/BP Sensor. Turn key off and wait 10 seconds. With breakout box installed and ECA connected, disconnect MAP/BP sensor. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin 26 and 46. If reading is 4.0 volts or higher, replace MAP/BP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 4.0 volts, go to next step.
8. With breakout box installed and ECA disconnected, turn key off and wait 10 seconds. Disconnect TPS, MAP/BP, and EVP sensor. Set DVOM on 200-ohm scale. Measure resistance between test pin 26 and test pins 20, 40, 46, and 60. If reading is less than 5 ohms, repair short to ground, connect all sensors and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If original problem still occurs, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 5 ohms or higher, connect sensors, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Reference Voltage Circuits. Scheme 44

TEST D - AIR CHARGE TEMPERATURE (ACT) SENSOR

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: cooling system, improper engine oil level, air cleaner duct problem. Ambient air temperature must be at least 50°F (10°C) for test results to be valid. Avoid performing test in unusually hot or cold conditions.

AIR CHARGE TEMPERATURE (ACT) SENSOR RESISTANCE

1. Code 24 Displayed. For vehicles with ACT sensor mounted in intake manifold, go to next step. If sensor is properly mounted in air cleaner on all other models, go to next step. If sensor is not properly mounted, install ACT sensor properly and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
2. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , Step 1). If reading is between 4.0 and 6.0 volts, connect TPS and go to next step.
3. Start engine and make sure that engine reaches normal operating temperature. Turn key off and wait 10 seconds. Disconnect ACT sensor, set DVOM on 200,000-ohm scale, and measure ACT sensor resistance. If reading is less than 1100 ohms or more than 58,000 ohms, check function of heat stove duct valve. If valve is operating correctly, replace ACT sensor, connect ACT sensor, and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is between 1100 and 58,000 ohms, go to next step.
4. Turn key off. Disconnect ACT sensor harness. Set DVOM on 200,000-ohm scale and run engine for 2 minutes. While engine is running, measure ACT sensor resistance. If reading is between 2400 and 29,000 ohms, replace ECA, connect ACT harness, and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 2400 ohms or more than 29,000 ohms, check function of heat stove duct valve. If valve works properly, replace ACT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Code 54 Displayed. Turn key off and wait 10 seconds. Disconnect ACT sensor harness. Inspect for and repair any damaged wiring. Install a jumper wire between ACT signal and signal return at connector. Perform KEY ON/ENGINE OFF SELF-TEST. If code 64 is displayed, replace ACT sensor. Remove jumper wire, connect ACT sensor, and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 64 is not displayed, remove jumper wire and go to next step.
6. Turn key off and wait 10 seconds. Leave ACT sensor harness disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 25 and ACT signal at ACT connector, and between test pin 46 and signal return at ACT connector. If both readings are less than 5 ohms, replace ECA and remove breakout box. Connect ECA and ACT sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If either reading is 5 ohms or higher, repair opens in circuit. Remove breakout box, connect ECA and ACT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
7. Code 64 Displayed. Turn key off and wait 10 seconds. Disconnect ACT sensor. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST. If code 54 is displayed, replace ACT sensor, connect harness, and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 54 is not displayed, go to next step.
8. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , Step 1). If reading is between 4.0 and 6.0 volts, connect TPS and go to next step.
9. Turn key off and wait 10 seconds. Disconnect harness at ACT sensor. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200,000-ohm scale. Measure resistance between test pin 25 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair shorts. Remove breakout box, connect ECA and ACT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 10,000 ohms or higher, replace ECA. Remove breakout box, connect ECA and ACT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
10. Continuous Code 54 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for indication of fault while tapping ACT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace ACT sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
11. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , wiggle and bend small sections of harness from ACT sensor to firewall. Repeat action from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
12. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious damage. If connector and terminals are damaged, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connector and terminals are okay, fault cannot be duplicated at this time, continuous code 54 testing is complete.

Air Charge Temperature (ACT) Sensor Circuit. Scheme 45

TEST E - EVP, EGRC & EGRV

To prevent replacement of good components, be aware that the following non-EEC related area may be at fault: damaged EGR valve.

1. Code 31 Displayed. Turn key off and wait 10 seconds. Disconnect and plug vacuum line at EGR valve. Perform ENGINE RUNNING SELF-TEST. Check for code 31. If code 31 is not displayed but codes 32 and 34 are, go to step 8). If code 31 is displayed, go to next step.
2. Turn key off and wait 10 seconds. Leave EGR vacuum line disconnected and plugged. Disconnect EVP sensor harness. Set DVOM on 200,000-ohm scale and connect vacuum pump to EGR valve. Measure resistance between EVP signal and VREF at EVP connector while vacuum is slowly increased to 10 in. Hg. If reading is less than 100 ohms or more than 5500 ohms, replace EVP sensor, connect vacuum signal line and harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading does not decrease or valve does not hold vacuum, go to step 14). If reading gradually decreases from a maximum of 5500 ohms to a minimum of 100 ohms, go to next step.
3. Turn key on, leaving engine off. Disconnect and plug vacuum signal line and disconnect EVP sensor harness. Set DVOM on 20 volt scale. Measure voltage between VREF and signal return at EVP connector. If reading is less than 4.0 volts or higher than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , Step 1). If reading is between 4.0 and 6.0 volts, go to next step.
4. Turn key off and wait 10 seconds. Disconnect harness at EVP sensor and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 27 and EVP signal at EVP connector. If reading is 5 ohms or higher, repair open in circuit. Remove breakout box, connect ECA and EVP sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
5. Turn key off and disconnect harness at EVP sensor. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 27 and test pins 26, 40, 46, and 60. If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, connect ECA and EVP sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 10,000 ohms or higher, go to next step.
6. Turn key off and wait 10 seconds. Connect known good EVP sensor and EGR valve assembly to harness and vacuum lines. Remove breakout box and connect ECA. Perform KEY ON/ENGINE OFF SELF-TEST. If code 31 is displayed, replace ECA. Connect original EVP sensor and EGR valve assembly. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 31 is not displayed, go to next step.
7. Turn key off and wait 10 seconds. Install original EVP sensor to known good EGR valve. Connect EVP sensor and perform KEY ON/ENGINE OFF SELF-TEST. If code 31 is displayed, replace EVP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 31 is not displayed, service EGR system.
8. Codes 32, 33, or 34 Displayed. Use DVOM for this step, do not use STAR tester. Turn key off and wait 10 seconds. Set DVOM on 20 volt scale. Connect DVOM negative test lead to STO and positive lead to battery positive post. Connect jumper wire between STI and signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads 0 volts). Depress and release throttle. If reading does not change to high voltage, depress throttle to WOT and release. If STO voltage does not go high, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , Step 17). If DVOM reading does go high, stay in OUTPUT STATE CHECK and go to next step.
9. Turn key on, leaving engine off. Stay in OUTPUT STATE CHECK with DVOM set to 20-volt scale. Connect DVOM between EGRV solenoid, VPWR and EGRV signal. Depress and release throttle several times to cycle output on and off while observing DVOM. Repeat check for EGRC solenoid, VPWR and EGRC signal. If either solenoid does not cycle on and off, exit OUTPUT STATE CHECK and go to step 15). If both solenoids cycle on and off, stay in OUTPUT STATE CHECK and go to next step.
10. Turn key on, leaving engine off. Stay in OUTPUT STATE CHECK. Disconnect and plug vacuum line from bottom port of EGRC solenoid. Connect vacuum pump to open port. Connect vacuum gauge in common output (upper) vacuum line to EGR valve. Disconnect, but DO NOT plug vacuum vent line from EGRV solenoid. Maintain source vacuum and cycle output on and off by depressing and releasing throttle.
11. If vacuum does not cycle on and off in less than 2 seconds, check solenoid filter for obstructions, and replace if necessary. If filter is okay, replace solenoid assembly. After repairs, connect all vacuum lines and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum output cycles on and off in less than 2 seconds, connect all vacuum lines and go to next step.
12. Turn key off and wait 10 seconds. Connect all vacuum lines, and check vacuum lines for proper routing, kinks, cracks, obstructions, leaks, etc. Use vehicle emissions decal as a guide. If vacuum lines are not okay, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum lines are okay, go to next step.
13. With key off, disconnect EVP sensor harness. Inspect for and repair any damaged wiring. Set DVOM on 200,000-ohm scale. Disconnect vacuum line at EGR valve and connect vacuum pump to valve. Measure resistance of EVP sensor between EVP signal and VREF terminals while increasing vacuum to 10 in. Hg. If reading slowly decreases from maximum of 5500 ohms to minimum of 100 ohms, replace ECA. Connect EVP sensor and EGR vacuum line. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading does not slowly decrease, go to next step.
14. With key off and harness disconnected from EVP sensor. Remove EVP sensor and vacuum line from EGR valve. Measure resistance of EVP sensor between EVP signal and VREF terminals. Observe resistance changes as EVP sensor shaft is slowly pushed in and slowly released. If both readings increase and decrease smoothly in range of 100-5500 ohms, replace EGR valve assembly. Connect EVP sensor and EGR vacuum line. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If either reading changes abruptly during range of 100-5500 ohms, replace EVP sensor. Reconnect harness and EGR vacuum line. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . It is normal for EVP sensor total resistance to drop below 100 ohms when disconnected from EGR valve. A defective part will change resistance SUDDENLY between 5500 and 100 ohms.
15. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect EGRC and EGRV solenoids from harness. Inspect for and repair any damaged wiring. Measure resistance of both solenoids. If either reading is less than 30 ohms or more than 70 ohms, replace EGRC/EGRV solenoid assembly. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are between 30 and 70 ohms, reconnect solenoids and go to next step.
16. Disconnect EGRC and EGRV solenoids from harness. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between battery negative terminal and VPWR circuit for both solenoids. If either reading is less than 10.5 volts, repair open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10.5 volts or more, go to next step.
17. Turn key off and wait 10 seconds. Leave EGRC and EGRV solenoids disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 33 and EGRV signal at EGRV solenoid connector. Measure resistance between test pin 52 and EGRC signal at EGRC solenoid connector. If either reading is 5 ohms or more, repair open circuit. Remove breakout box, connect ECA and solenoids, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are less than 5 ohms, go to next step.
18. Turn key off and wait 10 seconds. Set DVOM on 200,000-ohm scale. Install breakout box, leaving ECA disconnected. Disconnect EGRC and EGRV solenoids. Measure resistance between test pin 33 and/or 52 and test pins 40, 46, and 60. If readings are less than 10,000 ohms, repair short to ground. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are 10,000 ohms or more, go to next step.
19. With key off, disconnect EGRC and EGRV solenoids from harness. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 33 and test pins 37 and 57. Measure resistance between test pin 52 and test pins 37 and 57. If any reading is less than 10,000 ohms, repair short in circuit. Remove breakout box and connect ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA. If all readings are 10,000 ohms or more, replace ECA. Remove breakout box and connect ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
20. Code 35 Displayed. This code indicates that engine RPM is too low for correct EGR testing. If code 12 is also displayed, go to «TEST X - IDLE SPEED CONTROL (BY-PASS AIR)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-x-idle-speed-control) , step 1) for EFI models with air by-pass. If code 12 is not displayed with code 35, go to next step.
21. Turn key off and wait 10 seconds. Install tachometer. Perform ENGINE RUNNING SELF-TEST at 1500 RPM. Record ENGINE RUNNING service codes. If code 35 is displayed, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 35 is not displayed, repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) and repair codes as necessary.
22. CONTINUOUS Code 31 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for indication of fault while doing the following: connect vacuum pump to EGR valve. Very slowly apply 6 in. Hg vacuum to EGR valve. Bleed vacuum slowly and lightly tap on EVP sensor. Wiggle EVP sensor connector. If fault is indicated, go to next step. If no fault is indicated, go to step 24).
23. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Stay in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) . Connect DVOM between test pins 27 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Repeat step 22) while watching voltage. If fault occurs below 4.25 volts, disconnect EVP sensor from harness. Inspect connector and terminals. If connector and terminals are okay, replace EVP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault does not occur below 4.25 volts, EGR valve overshoot may have caused continuous code 31. Sensor test is complete. Go to next step for harness test.
24. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , bend, shake, and wiggle small sections of EEC-IV harness from sensor to firewall and from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
25. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connector and terminals are okay, fault cannot be duplicated at this time. Continuous code 31 testing is complete.

EVP, EGRC & EGRV Solenoid Circuits. Scheme 46

TEST F - ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Note. For purposes of this test, a "warmed up" engine has a coolant temperature of 50-240°F (10-116°C) for KEY ON/ENGINE OFF SELF-TEST and 180-240°F (82-116°C) for ENGINE RUNNING SELF- TEST. The test procedure will be invalid outside these ranges.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: Coolant or oil level. Blocked or obstructed air flow. Engine not at normal operating temperature, cooling fan.

1. Code 21 Displayed. Start and run engine at 2000 RPM for 2 minutes. Check that upper radiator hose is hot and pressurized. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) before continuing. If vehicle stalls, DO NOT service code 21 at this time, go directly to «DIAGNOSIS BY SYMPTOM TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__diagnosis-by-symptom-test) . If code 21 is not displayed, service other codes as necessary (if displayed). If code 21 appears, go to next step.
2. Turn key off and wait 10 seconds. Disconnect TPS. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at TPS harness connector between VREF and signal return. If voltage is less than 4.0 volts or higher than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If voltage is between 4 and 6 volts, reconnect TPS and go to next step.
3. Make sure engine is fully warmed up for this step. Turn key off and wait 10 seconds. Disconnect wiring harness at ECT sensor. Set DVOM on 200,000-ohm scale and measure resistance of ECT sensor. If reading is 1300-7700 ohms at engine coolant temperature of 240-140°F (116-60°C) with engine off and 1550-4550 ohms at 230-180°F (110-82°C) with engine running, replace ECA, connect ECT sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are not correct for coolant temperature, replace ECT sensor, connect harness, and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
4. Code 51 Displayed. Turn key off and wait 10 seconds. Disconnect ECT sensor at wiring harness and inspect wiring for damage or corrosion. Connect a jumper wire between ECT signal and signal return terminals in sensor harness connector. Repeat KEY ON/ENGINE OFF SELF-TEST. If code 61 is displayed, replace ECT sensor and remove jumper wire. Connect harness to ECT sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 61 is not displayed, go to next step.
5. Turn key off and wait 10 seconds. With harness disconnected at ECT sensor and jumper removed from harness connector, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between ECT signal at ECT connector and test pin 7. Measure resistance between signal return at ECT connector and test pin 46. If both readings are less than 5 ohms, replace ECA. Remove breakout box and connect ECA and ECT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If either reading is 5 ohms or higher, repair open circuits. Remove breakout box, connect ECA and ECT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
6. Code 61 Displayed. Turn key off and wait 10 seconds. Disconnect ECT sensor and inspect connector for damage or corrosion. Repair wiring and repeat KEY ON/ENGINE OFF SELF-TEST. If code 51 is displayed, replace ECT sensor, connect sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 51 is not displayed, go to next step.
7. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0 volts or higher than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If voltage is between 4.0 and 6.0 volts, connect TPS and go to next step.
8. Turn key off and wait 10 seconds. Disconnect harness from ECT sensor. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 7 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short circuits. Remove breakout box, connect ECA and ECT sensor, then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 10,000 ohms or higher, replace ECA. Remove breakout box, connect ECA and ECT sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
9. CONTINUOUS Code 21 Displayed. Turn key off and wait 10 seconds. Disconnect all SELF-TEST equipment and prepare vehicle for test drive. While driving vehicle, attempt to copy driving style in which complaint was noticed. If problem occurs, try to maintain condition for 1 or more minutes. After road test, repeat KEY ON/ENGINE OFF SELF-TEST. If code 21 is present in «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) , make sure that thermostat is working properly. If thermostat functions properly, replace ECT sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 21 is not displayed, fault cannot be duplicated at this time. Continuous code 21 testing is complete.
10. CONTINUOUS Code 51 or 61 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED while tapping ECT sensor and wiggling ECT connector. If fault is indicated, disconnect and inspect ECT connector and terminals. If connector and terminals are okay, replace ECT sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
11. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for fault as you bend, shake or wiggle EEC-IV harness. Start at sensor connector and work toward firewall. Also test harness from firewall to ECA in same manner. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault is not indicated, go to next step.
12. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connector and terminals are okay, fault cannot be duplicated at this time. Continuous code 51 or 61 testing is complete.

Engine Coolant Temperature (ECT) Sensor Circuit. Scheme 47

TEST G - MAP/BP SENSOR

Note. Barometric pressure sensor output is digital and must be measured with MAP/BP tester.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: Unusually high/low atmospheric barometer reading. Kinked or blocked vacuum lines. Engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.).

Scheme 48

1. Code 22 Displayed, Engine Off. Turn key off. Disconnect MAP/BP sensor from harness. Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. Go to next step. (Scheme 48): Correct Hookup For MAP/BP Tester
2. With MAP/BP tester connected, turn key on. If only Green light on tester is lit, VREF is correct. Go to step 4). If "less than 4 volts" Red light or no lights come on, VREF is too low. If "more than 6 volts" Red light comes on, VREF is too high. If VREF is too high or too low, go to next step.
3. With MAP/BP tester connected, turn key on. Disconnect MAP/BP sensor and repeat step 2). If only Green light comes on, VREF is correct. Replace MAP/BP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If "less than 4 volts" Red light or no lights come on, VREF is too low. If "more than 6 volts" Red light comes on, VREF is too high. If VREF is too high or too low, remove MAP/BP tester, connect sensor, then go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage), step 1).
4. With MAP/BP tester connected and key on, measure sensor output voltage. If voltage output is in correct range for altitude of vehicle being tested, go to next step. If output reading is outside range, go to step 6). NOTE: Measure several known good MAP/BP sensors on available vehicles. Mean voltage reading will be typical for your location on date of testing. MAP VOLTAGE OUTPUT Elevation (Ft.) Voltage Output (Volts) 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43 MAP SENSOR FREQUENCY Manifold Vacuum (In. Hg) Frequency (Hz) kPa 0 159 0.00 3 150 10.2 6 141 20.3 9 133 30.5 12 125 40.6 15 117 50.8 18 (curb idle) 109 61.0 21 (curb idle) 102 71.1 24 95 81.3 27 88 91.5 30 80 101.6
5. Turn key off and wait 10 seconds. Disconnect MAP/BP sensor from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between MAP/BP signal at sensor connector and test pin 45. If reading is less than 5 ohms, replace ECA. Connect ECA and MAP/BP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is 5 ohms or higher, repair opens in wiring. Remove breakout box, connect ECA and MAP/BP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
6. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Disconnect harness at MAP/BP sensor. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 45 and test pins 26, 46, 40, and 60. If any reading is less than 10,000 ohms, repair shorts in wiring. Remove breakout box and connect ECA and MAP/BP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If all readings are 10,000 ohms or higher, replace MAP/BP sensor. Remove breakout box and connect all wiring. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
7. Code 22 Displayed, Engine Running. Turn key off and wait 10 seconds. Disconnect vacuum line from MAP sensor. Hook vacuum pump to MAP sensor and apply 18 in. Hg. vacuum to sensor. If sensor does not hold vacuum, replace MAP sensor, connect vacuum line and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If MAP sensor does hold vacuum, go to next step.
8. Turn key off and wait 10 seconds. Plug vacuum supply hose to MAP sensor. Start engine and hold in 1400-1600 RPM range. Slowly apply 15 in. Hg vacuum to MAP sensor. Perform ENGINE RUNNING SELF-TEST while holding RPM range. Ignore all other codes at this time. If code 22 is still displayed, replace MAP sensor. Connect vacuum hose and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If code 22 is not displayed, check vacuum hose to sensor and repair. If hose is good, service other codes as necessary, then check engine for low vacuum condition.
9. Turn key off and wait 20 seconds. Plug vacuum supply hose to MAP sensor. Start engine and hold in 1400-1600 RPM range. Slowly apply 15 in. HG vacuum to MAP sensor. Perform ENGINE RUNNING SELF-TEST while holding RPM range. Ignore all other codes at this time. If code 22 is still displayed, replace MAP sensor. Connect vacuum hose and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If code 22 is not displayed, check vacuum hose to sensor and repair. If hose is good, service other codes as necessary. Check engine for low vacuum condition.
10. Code 72 Displayed. Turn key off and wait 10 seconds. Install vacuum gauge with "T" in manifold vacuum line at MAP sensor. Perform ENGINE RUNNING SELF-TEST and observe vacuum reading before and during DYNAMIC RESPONSE CHECK portion of test. Record service codes. If vacuum decreased 10 in. Hg or more and code 72 is not displayed, disconnect vacuum gauge and service other codes as necessary. If vacuum decreased 10 in. Hg and code 72 is displayed, replace MAP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If vacuum decreased less than 10 in. Hg, go to next step.
11. Check vacuum lines for correct routing, using vehicle emissions decal as a guide. Also check MAP sensor vacuum lines for kinks or blockage. If lines are good, EEC-IV system is okay. Check engine for cause of low vacuum. If vacuum lines are bad, repair as necessary and repeat step 10).
12. Turn key off. Disconnect MAP/BP sensor from harness. Connect MAP/BP tester between wiring harness and MAP/BP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. Go to next step.
13. Turn key on and measure sensor output. Compare values to «MAP VOLTAGE OUTPUT»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table. If reading is out of range, replace MAP/BP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is within range, go to next step.
14. Check MAP sensor vacuum lines for leaks, bad connections, kinks or blockage. If vacuum lines are okay, go to «DIAGNOSIS BY SYMPTOM TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__diagnosis-by-symptom-test). If vacuum lines are bad, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
15. CONTINUOUS Code 22 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test), observe VOM or STAR tester LED for indication of fault while doing the following: connect vacuum pump to MAP sensor and slowly apply 25 in. Hg. Bleed vacuum slowly, tap MAP sensor lightly, and wiggle MAP connector. If fault is indicated, disconnect sensor. Inspect connector and terminals for damage. If connector and terminals are okay, replace MAP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If no fault is indicated, go to next step.
16. Stay in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test). Observe VOM or STAR tester LED for indication of fault while shaking, bending or wiggling small sections of harness from sensor connector to firewall. Check harness from firewall to ECA in same manner. If fault is indicated, isolate fault in harness and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If no fault is indicated, go to next step.
17. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and terminals for obvious damage. If connector and terminals are damaged, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If connector and terminals are okay, fault cannot be duplicated at this time. Continuous code 22 testing is complete.

MAP/BP Sensor Circuit. Scheme 49

TEST H - KNOCK SENSOR

Note. Use DYNAMIC RESPONSE CHECK as specified in steps 1) and 6). There is no need to perform WOT during this test. For additional information see QUICK TEST DIAGNOSTIC AID, DYNAMIC RESPONSE CHECK.

To prevent replacement of good components, be award that the following non-EEC related areas may be at fault: fuel quality, engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.) and spark timing.

1. Code 25 Displayed. Have 4 oz. hammer ready. Perform ENGINE RUNNING SELF-TEST. When DYNAMIC RESPONSE CHECK signal appears, lightly tap above Knock Sensor (KS) with 4 oz. hammer. After 15 seconds, check for code 25. Ignore all other codes at this time. If code 25 is displayed, go to next step. If code 25 is not displayed, knock system is okay. Repeat ENGINE RUNNING SELF-TEST and service other codes.
2. Turn key off and wait 10 seconds. Disconnect knock sensor. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at knock sensor connector between KS signal and signal return. If reading is higher than 4 volts, go to step 5). If voltage is between 1 and 4 volts, go to step 6). If reading is less than 1 volt, go to next step.
3. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and knock sensor disconnected. With DVOM on 200-ohm scale, measure resistance between knock sensor connector signal return and test pin No.46, and between knock sensor connector KS signal and test pin No. 23. If either reading is 5 ohms or more, service open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are less than 5 ohms, go to next step.
4. Turn key off and wait 10 seconds. With breakout box installed, ECA and knock sensor disconnected, set DVOM on 200,000-ohm scale. Measure resistance between knock sensor connector KS signal and test pins No. 40, 46 and 60. If all readings are 10,000 ohms or higher go to step 6). If any reading is less than 10,000 ohms, repair shorts in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Turn key off and wait 10 seconds. With breakout box installed, ECA and knock sensor disconnected, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between test pins No. 23 and 40. If reading is 0.5 volt or more, repair knock sensor harness short to power, and then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 0.5 volt, go to next step.
6. Turn key off and wait 10 seconds. Remove breakout box and connect ECA. Connect substitute knock sensor (same Part No.) into harness but do not install in engine. Perform ENGINE RUNNING SELF-TEST. When DYNAMIC RESPONSE CHECK signal appears, lightly tap knock sensor with 4 oz. hammer. If code 25 appears 15 seconds later, replace ECA. Remove substitute knock sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) with original sensor. If code 25 does not appear 15 seconds later, install new knock sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Knock (Detonation) Sensor Circuit. Scheme 50

TEST I - THROTTLE POSITION SENSOR (TPS)

To prevent replacement of good components, be aware the following non-EEC related areas may be a fault: idle speed/throttle stop adjustment, binding throttle shaft/linkage or cruise control linkage, or choke/high cam system (if equipped).

1. Code 23 Displayed. If KEY ON/ENGINE OFF SELF-TEST code 68 or ENGINE RUNNING SELF-TEST codes 31, 41 or 58 are displayed, service these codes first. Disregard code 23 at this time. If these codes have been serviced or are not displayed, go to next step.
2. Inspect throttle body and linkage for mechanical binding or sticking. Make sure linkage is set with throttle in closed position. If throttle plate or linkage is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair problem(s) and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no mechanical problem is found, go to next step.
3. Turn key off and wait 10 seconds. Disconnect TPS from harness at throttle body. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST. Check for code 63. Ignore all other codes at this time. If code 63 is not displayed, go to step 5). If code 63 is displayed, go to next step.
4. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS from harness. Inspect for and repair any damaged wiring. Turn key on, leaving engine off. Measure voltage at TPS connector between VREF and signal return. If reading is less than 4 volts or higher than 6 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If reading is between 4 and 6 volts replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Turn key off and wait 10 seconds. Disconnect TPS from harness. Set DVOM on 200,000-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between test pin No. 47 and test pins No. 26 and 57. If either reading is less than 10,000 ohms, repair short in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or higher, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
6. Code 63 Displayed. Turn key off and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TPS signal at connector. Perform KEY ON/ENGINE OFF SELF-TEST. Check for codes 53 or 23, ignore all other codes at this time. If no codes are displayed, immediately remove jumper wire, and go to step 9). If either code 53 or 23 are displayed, replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If neither code 53 or 23 are displayed, go to next step.
7. Turn key off and wait 10 seconds. Disconnect TPS from harness. Inspect for and repair any damaged wiring. Set DVOM on 20 volt scale. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4 volts or more than 6 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If reading is between 4 and 6 volts, go to next step.
8. Turn key off and wait 10 seconds. Leave TPS disconnected. Set DVOM on 200-ohm scale and disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Measure resistance between TPS signal at connector and test pin No. 47. If reading is 5 ohms or more, repair faulty circuit. Remove breakout box, connect ECA and TPS, and then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
9. Turn key off and wait 10 seconds. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200,000-ohm scale. Measure resistance at connector between TPS signal and ground, and between TPS signal and test pin No. 46. If either reading is less than 10,000 ohms, repair short circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or more, replace ECA. Remove breakout box, connect TPS, and then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . NOTE: Code 73 in step 10) indicates that TPS did not exceed 25% of its rotation during DYNAMIC RESPONSE CHECK. For additional information see QUICK TEST DIAGNOSTIC AIDS, DYNAMIC RESPONSE CHECK.
10. Code 73 Displayed. Turn key off. Install breakout box and set DVOM on 20-volt scale. Connect DVOM to test pins No. 46 and 47. Perform ENGINE RUNNING SELF-TEST. Verify that DVOM reading exceeds 3.5 volts during WOT of DYNAMIC RESPONSE CHECK. If reading exceeds 3.5 volts, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading does not exceed 3.5 volts, make sure that TPS is correctly installed and adjusted. If okay, replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
11. CONTINUOUS Code 53 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or diagnostic tester LED for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position and lightly tap TPS and wiggle connector. If no fault is indicated, go to step 13). If fault is indicated, go to next step.
12. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA connected. Stay in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) and connect DVOM between test pins No. 47 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Observe DVOM and repeat step 11). If fault occurs below 4.25 volts, inspect TPS connectors and terminals. If okay, replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault does not occur below 4.25 volts, TPS over-travel may have caused continuous code 53. TPS is good, go to next step to check harness.
13. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , shake, bend and wiggle small sections of EEC-IV harness from TPS sensor to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, to next step.
14. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 53 testing is complete.
15. CONTINUOUS Code 63 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or diagnostic tester LED for indication of fault while slowly opening throttle to WOT. slowly bring throttle to closed position and lightly tap TPS and wiggle connector. If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
16. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , shake, bend and wiggle small sections of EEC-IV harness from TPS sensor to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
17. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 63 testing is complete.

Throttle Position Sensor (TPS) Circuit. Scheme 51

TEST J - PRESSURE FDBK EGR (PFE) & EGR VALVE REGULATOR (EVR)

1. Code 31 Displayed. Turn key off. Disconnect PFE harness at sensor. Install a jumper wire between VREF and PFE signal at sensor connector. Perform KEY ON/ENGINE OFF SELF-TEST. Check for code 35. Ignore all other codes at this time. If no codes are displayed, immediately remove jumper wire and go directly to step 4). If code 35 is displayed, remove jumper wire and replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 35 is not displayed, go to next step.
2. With key off and PFE harness disconnected, set DVOM on 20 volt scale. Turn key on, leaving engine off. Measure voltage at PFE connector between VREF and signal return. If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If reading is between 4.0 and 6.0 volts, go to next step.
3. With key off and PFE harness disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between PFE signal at connector and test pin No. 27. If reading is 5 ohms or higher, repair faulty circuit. Connect PFE sensor and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
4. With key off and PFE harness disconnected, install breakout box leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between ground and PFE signal at connector. Measure resistance between PFE signal at connector and test pin No. 46. If either reading is less than 10,000 ohms, repair short circuit. Connect PFE and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or more, replace ECA. Connect PFE and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Code 35 Displayed. Turn key off and disconnect PFE harness at sensor. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST. Check for code 31. Ignore all other codes at this time. If code 31 is not displayed, go to step 7). If code 31 is displayed, go to next step.
6. With key off and PFE harness disconnected, set DVOM on 20 volt scale. Turn key on, leaving engine off. Measure voltage at PFE connector between VREF and signal return. If reading is between 4.0 and 6.0 volts, replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1).
7. With key off and PFE harness disconnected, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pins No. 27, 26 and 57. If either reading is less than 10,000 ohms, repair short. Connect PFE and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or higher , replace ECA. Connect PFE and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
8. Code 34 Displayed. The PFE system can detect lack of pressure in exhaust system. An efficient garage exhaust ventilation system, installed during KEY ON/ENGINE OFF SELF-TEST may cause PFE sensor to generate code 34. Remove exhaust ventilation system and retest. If code 34 is not displayed, service other codes displayed during KEY ON/ENGINE OFF SELF-TEST. If none, continue with «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 is displayed, go to next step.
9. Remove pressure feed tube from PFE sensor. Inspect complete tube, including PFE inlet for blockage. If blockage is found, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no blockage is found, go to next step.
10. Turn key off and disconnect PFE sensor. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at PFE connector between VREF and signal return. If reading is between 4.0 and 6.0 volts, replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1).
11. Code 84 Displayed. Turn key off. Set DVOM on 200-ohm scale. Disconnect EVR solenoid connector and measure solenoid resistance. If reading is less than 30 ohms or more than 70 ohms, replace EVR solenoid assembly. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is between 30 and 70 ohms, go to next step.
12. With key off and EVR solenoid disconnected from harness, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between negative battery terminal and VPWR circuit at EVR solenoid connector. If reading is less than 10.5 volts, repair VPWR open circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or more, go to next step.
13. Turn key off and disconnect EVR solenoid from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 33 and EVR signal at EVR solenoid connector. If reading is 5 ohms or more, repair open circuit. Connect EVR solenoid and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
14. Turn key off. Install breakout box, leaving ECA disconnected. Disconnect EVR solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 33, 37, 57, 40, 46 and 60 (ground). If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box. Connect ECA and EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA. If all readings are 10,000 ohms or more, replace ECA. Remove breakout box. Connect ECA and EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
15. Code 32 Displayed. The PFE system can detect lack of pressure in exhaust system. An efficient garage exhaust ventilation system, installed during ENGINE RUNNING SELF-TEST may cause PFE sensor to generate code 32. Remove exhaust ventilation system and retest. If code 32 is not displayed, service other codes displayed during ENGINE RUNNING SELF-TEST. If none, continue with «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 32 is displayed, go to next step.
16. Turn key off. Disconnect and plug EGR valve vacuum hose. Perform ENGINE RUNNING SELF-TEST. If code 31 or 32 are present, go to next step. If not, go to step 18.
17. With key off, check PFE sensor supply tube for blockage and/or leaks. If these faults are found, repair as necessary. Connect all lines and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no faults are found, service exhaust gas recirculation system.
18. Turn key off. Remove and inspect EVR filter for contamination. A blocked filter will cause vacuum to be applied to EGR valve prematurely. If filter is contaminated, replace filter. Connect all lines and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If filter is not contaminated, replace EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
19. Codes 34 or 35 Displayed. Service codes 34 and 35 in ENGINE RUNNING SELF-TEST indicate excessive exhaust backpressure. There are 2 possible causes: the exhaust system is blocked, or PFE sensor has shifted into high. Turn key off. Substitute known good PFE sensor in place of original. Repeat ENGINE RUNNING SELF-TEST. If code 34 or 35 is not displayed, replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 or 35 is displayed, check exhaust system for restrictions.
20. Code 33 Displayed. Turn key off. Using a "T", connect vacuum gauge at EGR valve. Perform ENGINE RUNNING SELF-TEST while observing vacuum gauge. Disregard code output. If vacuum reading is higher than 1 in. Hg, go to step 23). If vacuum reading is 1 in. Hg or less, go to next step.
21. With key off, check vacuum hose from EVR solenoid to EGR valve and from vacuum source to EVR solenoid for loose connections, obstructions, cracks, etc. If vacuum hoses are damaged, repair or replace as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If hoses are okay, go to next step.
22. Start engine. Attach vacuum gauge to EVR solenoid hose coming from engine manifold (vacuum source). If vacuum is present, replace EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no vacuum is present, replace vacuum hose to EVR solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
23. Turn key off. If control pressure input tube to PFE sensor is disconnected, blocked or cracked, repair or replace tube as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If tube is okay, replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
24. CONTINUOUS Code 31 or 35 Displayed. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or diagnostic tester LED for indication of fault while performing the following steps: connect a vacuum pump to PFE sensor, slowly apply 5 in. Hg vacuum to sensor, and then slowly bleed vacuum off PFE sensor. Lightly tap on PFE sensor and wiggle PFE connector. If fault is indicated, disconnect harness and inspect connector. If connector and terminals are okay, replace PFE sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
25. Observe VOM or diagnostic tester for fault indication while grasping harness closest to sensor connector, then wiggling, shaking or bending small sections of harness while working your way to firewall. Also wiggle, shake or bend harness from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault is not indicated, go to next step.
26. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connect. Inspect both connector and terminals for damage. If connector and terminals are damaged, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connector and terminals are okay, fault cannot be duplicated at this time. Continuous code 31 or 35 testing is complete.
27. CONTINUOUS Code 34 Displayed. Turn key off. Remove PFE sensor and inspect sensor supply inlet for liquids and/or any type of blockage. Inspect PFE supply tube at EGR valve base for liquids and/or blockage. If supply tube is blocked, clean or service as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If supply tube is not blocked, fault cannot be duplicated at this time. Continuous code 34 testing is complete.
28. CONTINUOUS Code 32 Displayed. Turn key off. Connect vacuum pump to EGR valve and apply 10 in. Hg of vacuum. While observing EGR valve, release vacuum, and repeat step if necessary. If EGR valve does not work smoothly, service exhaust gas recirculation system. If EGR valve works smoothly, go to next step.
29. Inspect EGR valve vacuum supply line from EVR solenoid for kinks and/or obstructions. If vacuum supply line is blocked, repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum supply line is okay, go to next step.
30. Carefully check EVR filter for contamination and/or obstructions. If EVR filter is contaminated, replace filter and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If EVR filter is not contaminated, fault cannot be duplicated at this time. Continuous code 32 testing is complete.
31. CONTINUOUS Code 33 Displayed. Turn key off. Connect a vacuum pump to EGR valve. While observing EGR valve, slowly apply 10 in. Hg of vacuum. EGR valve should begin to open at about 1 in. Hg and be fully open at 4 in. Hg of vacuum. If EGR does not move freely and smoothly, service exhaust gas recirculation system. If EGR moves freely and smoothly, go to next step.
32. With key off, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout, then connect ECA to box. Enter OUTPUT STATE CHECK. Set DVOM on 20-volt scale. Connect DVOM negative test lead to pin No. 40 and DVOM positive test lead on pin No. 33. Move throttle valve to indicate 10.5 volts or more and maintain position. While observing DVOM, grasp harness closest to EVR connector. Wiggle, shake or bend a small section of harness while working your way to firewall. Lightly tap EVR solenoid to simulate road vibration. If DVOM reads 10.5 volts or less, isolate fault and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If DVOM reads 10.5 volts or more, fault cannot be duplicated at this time. Continuous code 33 testing is complete.

Press. Feedback EGR (PFE) & EGR Valve Reg. (EVA) Circuits. Scheme 52

TEST K - VEHICLE SPEED SENSOR

Be aware that the following pinpoint test is to be used only when codes 27, or 29 are received in QUICK TEST .

1. Drive Cycle for Checking VSS. For automatic transmission equipped vehicles: record and clear EEC-IV SELF-TEST continuous codes. Warm engine to operating temperature. When in first gear accelerate moderately to 25 MPH and coast down to idle and stop. Shut off engine. Perform KEY OFF/ENGINE OFF test. Verify if code 29 is present. For manual transmission equipped vehicles: record and clear EEC-IV SELF-TEST continuous codes. Warm engine to operating temperature. Starting in first gear, shift to second gear and accelerate moderately to 40 MPH. Coast down to idle and stop. Shut off engine. Perform KEY OFF/ENGINE OFF SELF TEST. Verify if code 29 is present. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If codes are not present, test is completed. If code 29 is present, go to next step.
2. Sensor Check. Turn key off, wait 10 seconds. Disconnect vehicle speed sensor. Set DVOM on 200,000-ohm scale. Measure resistance across vehicle speed sensor. If resistance is not between 190-230 ohms, replace VSS sensor and repeat step 1). If resistance is between 190 and 230 ohms, go to next step.
3. Turn key off, wait 10 seconds. Remove ECA pin connector and inspect for damaged pins, corrosion, or loose wires. Repair and replace as necessary. Install breakout box. With ECA and VSS disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 3 at breakout box and VSS at vehicle harness. Measure resistance between test pin No. 6 at breakout box and VSS vehicle harness connector. If both resistances are 5 ohms or more, service open circuit in VSS harness and repeat test K, step 1). If resistance is 5 ohms or less, go to next step.
4. Turn key off and disconnect ECA. Set DVOM on 200,000-ohm scale. Measure resistance between pin No. 3 and pins No. 37, 40 and 6 at breakout box. Then measure resistance between pin No. 6 and pins No. 37 and 40 at breakout box. If readings are less than 10,000 ohms repair shorts and repeat step 1). If readings are greater than 10,000 ohms, go to next step.
5. Substitute VSS with known good sensor. Connect ECA and VSS. Repeat step 1), then return to this step. If code 29 is present, replace ECA and repeat step 1). If no codes are present, the original code 29 was result of faulty original VSS malfunction. Service VSS as necessary.

Vehicle Speed Sensor (VSS). Scheme 53

TEST L - EGR VALVE POSITION (EVP) & EGR VALVE REGULATOR (EVR)

1. Code 31 Displayed. Turn key off. Disconnect EVP harness at sensor. Install a jumper wire between VREF and EVP signal at sensor harness connector. Perform KEY ON/ENGINE OFF SELF-TEST. Check for code 35. Ignore all other codes at this time. If code 35 is displayed, replace EVP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 35 is not displayed, remove jumper wire and go to next step.
2. With key off and EVP disconnected, set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at EVP connector between VREF and signal return. If reading is less than 4.0 or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If reading is between 4.0 and 6.0 volts, go to next step.
3. With key off, and EVP disconnected, set DVOM on 200-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, then connect ECA to box. Measure resistance between EVP signal at connector and test pin 27. If reading is 5 ohms or more, repair open circuit. Connect EVP sensor and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
4. With key off and EVP harness disconnected, leave breakout box installed and ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between EVP signal at EVP connector and ground. Measure resistance between EVP signal at EVP connector and test pin 46. If either reading is less than 10,000 ohms, repair short circuit. Connect EVP and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or more, replace ECA. Connect EVP and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Code 35 Displayed. Turn key off. Disconnect EVP harness at sensor. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST. Check for code 31. Ignore all other codes at this time. If code 31 is not displayed, go to step 7). If code 31 is displayed, go to next step.
6. With key off and EVP harness disconnected, set DVOM on 20 volt scale. Turn key on, leaving engine off. Measure voltage at EVP harness connector between VREF and signal return. If reading is between 4.0 and 6.0 volts, replace EVP sensor. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 4.0 volts or more than 6.0 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1).
7. Turn key off and disconnect EVP from harness. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000 ohm scale. Measure resistance between test pin 27 and test pins 26 and 57. If either reading is less than 10,000 ohms, repair short in harness. Connect EVP sensor and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are 10,000 ohms or more, replace ECA. Connect EVP sensor and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
8. Code 84 Displayed. Turn key off. Set DVOM on 200-ohm scale. Disconnect EVR solenoid connector and measure solenoid resistance. If reading is less than 30 ohms or more than 70 ohms, replace EVR solenoid assembly. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is between 30 and 70 ohms, go to next step.
9. Leave EVR solenoid disconnected and set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between negative battery terminal and VPWR circuit at solenoid harness connector. If reading is less than 10.5 volts, repair VPWR open circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or higher, go to next step.
10. With key off and EVR solenoid disconnected, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 33 and EVR signal at EVR solenoid connector. If reading is 5 ohms or higher, repair open circuit. Connect EVR solenoid and remove breakout box. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
11. With key off, breakout box installed, and ECA and EVR solenoid disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin 33 and test pins 37, 57, 40, 46 and 60 (ground). If any reading is less than 10,000 ohms, repair short circuit. Remove breakout box, and connect ECA and EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA. If all readings are 10,000 ohms or more, replace ECA. Remove breakout box, and connect ECA and EVR solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
12. Code 34 KEY ON/ENGINE OFF. Test indicates EGR valve and/or EVP sensor is not fully seated in closed position. Because of preload on installed EVP sensor, it is hard to determine whether EGR valve is not seated, or EVP sensor is not in contact with EGR valve stem. Turn key off, wait 10 seconds. Install known good EVP sensor on original EGR valve. Perform KEY ON/ENGINE OFF «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 is present, problem is with EGR and should be diagnosed. If code 34 is not present, original code 34 was because EVP sensor was defective. Service EVP sensor as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
13. Code 32 KEY ON/ENGINE OFF and ENGINE RUNNING SELF/TEST. Test indicates EGR valve and/or EVP sensor is lower than normal in closed position. Because of preload of EVP sensor is difficult to determine whether EGR valve is defective or if EVP sensor has extremely high resistance. Turn key off, wait 10 seconds. Install known good EVP sensor on original EGR valve. Perform KEY ON/ENGINE OFF «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 32 is present, problem is with EGR and should be diagnosed. If code 32 is not present, original code 32 was the result of original EVP sensor. Service as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
14. Code 33 on ENGINE RUNNING. Test indicates EVP sensor reading did not change after EVR solenoid was instructed by ECA to open EGR valve. EGR valve is electrically capable as indicated by a pass code 11 in KEY ON/ENGINE OFF SELF-TEST and/or EVP sensor is in expected closed EGR valve range. Turn key off. Using "T" install vacuum gauge at EGR valve. Perform Engine running «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) while checking vacuum gauge. If vacuum gauge indicates 1.5 in Hg or greater vacuum, go to step 17). If vacuum gauge indicates less than 1.5 in. Hg of vacuum, go to next step.
15. Turn key off. Disconnect vacuum source to EVR solenoid. Install vacuum gauge at vacuum line and start engine. If vacuum reading is 10 in. Hg or less, check vacuum line for cracks or damage. If vacuum reading is 10 in. Hg or more, go to next step.
16. Carefully inspect vacuum line for cracks, loose connector, blockage, nicks and leaks. If vacuum line is good, check EGR solenoid filter for obstructions and replace as necessary. If filter is okay, replace EVR solenoid assembly and reconnect all vacuum lines. If vacuum lines are not good, service as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
17. Turn key off, wait 10 seconds. Install known good EVP sensor on original EGR valve. Perform ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 33 is present, EGR valve is defective and must be diagnosed. If code 33 is not present, original code 33 was result of original EVP sensor. EVP sensor should be serviced as necessary and «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) repeated.
18. Turn key off. Remove vacuum hose from EGR valve and plug hose. Perform ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 is not present, inspect EVR filter for damage or obstructions and replace as necessary. If okay, replace solenoid assembly. Reconnect all vacuum lines and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 is present, go to next step.
19. Turn key off. Remove harness from EVP sensor. Inspect for damaged pins, corrosion, and pins pushed out. Repair and replace as necessary. Set DVOM on 200,000-ohm scale. Remove vacuum line at EGR valve and connect vacuum pump. Measure resistance at EVP sensor between EVP signal and VREF while increasing vacuum to 10 in. Hg. Note resistance as vacuum increases. If resistance decreases gradually from no more than 5500 ohms to no less than 100 ohms, problem is with EGR and should be diagnosed. If resistance increases gradually, replace EVP sensor. ENGINE RUNNING SELF TEST code 38 indicates after operating EGR valve (during ENGINE RUNNING SELF-TEST) in EGR vacuum system was unable to maintain a specific (EVP) opening.
20. Turn key off. Check vacuum line from EVR solenoid to EGR valve for any leakage. If vacuum line is good, replace EVR solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum lines are not good, replace and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
21. Check Vacuum Line. Turn key off, wait 10 seconds. Be sure vacuum lines are reconnected. Check EGR vacuum line system from EGR valve for obstructions, kinks, leaks, etc. If lines are good, check EVR filter for obstructions. Replace as necessary. If okay, replace EVR solenoid. Reconnect all vacuum lines and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum lines are not in good condition, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
22. Code 32 CONTINUOUS Test. Code 32 indicates with engine at stabilized operating temperature and at idle, EVP circuit indicates that EGR valve is closed further than normal. Turn key off, wait 10 seconds. Remove 60 pin connector and inspect for damaged pins, corrosion or loose wires. Install breakout box and ECA. Connect vacuum pump to EGR valve. Connect DVOM from test pins No. 27 to 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Watch DVOM and very slowly apply 6 in. Hg vacuum to EGR valve. Slowly bleed vacuum off EGR valve and lightly tap on EVP sensor. If there are no voltage readings less than .29 volts test is completed. If readings above .29 volts are indicated, EGR valve may have caused continuous code 32. Service to sensor is not required, but EGR valve service is indicated.
23. Code 31 and/or Code 35 CONTINUOUS Test. Code 31 indicates, with engine at stabilized operating temperature and at idle, EVP circuit indicated an open or short to signal return Code 35 indicates, with engine at stabilized operating temperature and at idle, EVP circuit indicated a short to VREF and/or V power, or an open in signal return. Observe VOM or diagnostic tester for a fault while doing the following: wiggle, shake or bend a small section of the EEC IV harness closed to sensor connector. Check all wiring to dash panel. Also, wiggle and/or shake the EEC-IV harness from dash panel to ECA. If a fault is indicated, isolate and service as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault is not indicated, go to next step.
24. Turn key off, wait 10 seconds. Disconnect ECA 60 pin connector. Check both connectors for damage or faults. If connectors and terminals are okay, testing is complete. If not service and replace as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
25. Code 33 CONTINUOUS Test. Code 33 indicates, with engine at stabilized temperature and with a EVR solenoid duty cycle present, EGR valve did not open. Turn key off. Connect vacuum pump to EGR valve. If valve cannot maintain vacuum and stay open, valve may be defective and should be replaced. If it does stay open, go to next step.
26. Use continuous monitor mode and observe VOM or diagnostic tester for a fault while wiggling and bending a small section of harness while working your way to ECA. Inspect connectors and terminals for faults. If any faults are indicated, isolate and repair as necessary. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fault is not indicated, testing is complete.
27. Code 34 CONTINUOUS Test. Code 34 indicates, with engine at stabilized operating temperature and at idle, EGR valve is open. Turn key off. Disconnect harness from EVP sensor. Inspect for damaged pins, corrosion, etc. Set DVOM on 200,000-ohm scale. Disconnect vacuum line at EGR valve. Connect vacuum pump to EGR valve. Measure resistance at EVP sensor between EVP signal pin and VREF pin while increasing vacuum to 10 in. Hg. Observe resistance as vacuum increases. If reading does not decrease gradually, EGR valve is at fault and should be diagnosed. If reading gradually decreases from no more than 5500 ohms to no less than 100 ohms, go to next step.
28. Turn key off. Remove vacuum hose from EGR valve and plug hose. Perform ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 34 is not present, you are unable to duplicate fault at this time. If code 34 is present, check EVR filter for obstructions and replace as necessary. If okay, replace EVR solenoid and reconnect vacuum lines. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

EGR Valve Position (EVP) & EGR Valve Reg. (EVR) Circuits. Scheme 54

Scheme 55

Scheme 56

1. Code 67 Displayed. When this code is displayed, determine which engine and system is being tested and proceed to correct step as listed. For 2.3L EFI models with Man. Trans., go to step 5). For 2.9L & 3.0L EFI models, go to step 5). For 4.9L EFI models with Man. Trans., go to step 7). For all other models, go to next step.
2. Turn key off and wait 10 seconds. Make sure heater control is in "OFF" position and that transmission is in Neutral or Park. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Turn key on, leaving engine off. Set DVOM on 20-volt scale and measure voltage between test pin 30 and chassis ground. If reading is less than 1.0 volt, go to step 4). If reading is 1.0 volt or higher, go to next step.
3. Turn key off and wait 10 seconds. Leave breakout box installed and ECA connected. Locate neutral drive switch and disconnect harness at switch. Set DVOM on 200-ohm scale and measure resistance across switch. If reading is less than 5 ohms, repair open in neutral drive switch circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is 5 ohms or more, replace neutral drive switch and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
4. Install breakout box and connect ECA. Turn key on, leaving engine off. Set DVOM on 20-volt scale, and turn A/C control switch off. Measure voltage between test pin 10 and chassis ground. If reading is 1.0 volt or more, repair short to power in A/C clutch circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is less than 1.0 volt, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
5. Turn key off and wait 10 seconds. Make sure that A/C is off, if equipped. Ensure that transmission is in Neutral and that clutch is released. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. With DVOM on 200-ohm scale, measure resistance between test pins 30 and 46. If reading is less than 5 ohms, go to step 4). If reading is 5 ohms or more, go to next step.
6. Turn key off. With breakout box and ECA connected, set DVOM on 200-ohm scale. Locate neutral switch (on transmission) and clutch switch (under dash). Disconnect wiring harness from both switches. Measure resistance across each switch. If reading at both switches is less than 5 ohms, go to next step. If reading at either or both switches is 5 ohms or more, replace defective switch(es). Connect harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). (Scheme 55): Neutral Drive-A/C Input Ckt (2.3L EFI Man. Trans.), (2.9L & 3.0L EFI Models) (Scheme 56): Neutral Drive-A/C Input Ckt for All Other Models.
7. Turn key off. Set DVOM on 200-ohm scale and install breakout box. Disconnect vehicle harness at neutral switch and clutch switch. Measure resistance between pin No. 30 and neutral switch harness connector and between pin No. 46 and clutch switch harness connector. Also measure resistance between pin No. 46 and neutral switch harness connector and between pin No. 46 and clutch switch harness connector. If readings are more than 5 ohms, repair harness/connector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If readings are less, repeat step 4).
8. Clutch Pedal Switch Test 4.9L M/T. Turn key off and wait 10 seconds. Depress clutch pedal. Verify that A/C switch is off (if equipped). Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Set DVOM on 20 volt scale. Measure resistance between test pin No. 30 and neutral input circuit at SELF-TEST connector. If reading is less than 5 ohms, go to step 4). If reading is 5 ohms or more, repair open in clutch circuit.
9. A/C Input Circuit Check. Turn key off, wait 10 seconds. Remove ECA pin connector and inspect for damage. Repair as necessary. Install breakout box but leave ECA disconnected. Set DVOM on 20-volt scale. Turn key on and turn on A/C. Check voltage between pins No. 10 and 40. If voltage is greater than 10.5 volts, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If voltage is lower than 10.5 volts, service open in A/C circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).

Neutral Drive-A/C Input Ckt for 4.9L EFI (M/T) Models. Scheme 57

TEST O - BRAKE ON/OFF (BOO) SWITCH

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: brake lamp bulb, brake lamp switch, or brake lamp fuse.

1. Code 74 Displayed. If brake was NOT pressed during ENGINE RUNNING SELF-TEST, repeat test and press brake pedal once during test. If pedal was pressed, go to next step.
2. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pin 2 and 40 while applying and releasing brake. If voltage cycles, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If voltage does not cycle, go to next step.
3. Turn key off. Leave breakout box installed and ECA disconnected. Set DVOM on 200-ohm scale. Disconnect BOO circuit at 12 pin connector. Measure resistance between test pin 2 and ground. If reading is less than 5 ohms, repair BOO circuit short to ground. If reading is greater than 5 ohms, go to step 6).
4. Code 75 Displayed. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pin 2 and 40 while applying and releasing brake. If voltage cycles, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If voltage does not cycle, go to next step.
5. Turn key off. With breakout box installed and ECA disconnected, set DVOM on 20-volt scale. Disconnect BOO circuit at 12 pin connector. Measure voltage between test pin 2 and engine block ground. If reading is greater than 10.5 volts, repair BOO circuit short to power. If reading is less than 10.5 volts, BOO circuit is okay. Check brake lamp circuit.
6. Turn key off. With breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Disconnect BOO circuit from 12 pin connector. Measure resistance between test pin No. 2 at breakout box and BOO circuit at 12 pin connector. If resistance reading is greater than 5 ohms, service BOO circuit for possible open circuit. Repeat ENGINE RUNNING SELF-TEST. If resistance is less than 5 ohms, service BOO circuit for short. Repeat ENGINE RUNNING SELF-TEST. If reading is less, BOO circuit is okay.

Brake ON/OFF (BOO) Circuit. Scheme 58

TEST P - POWER STEERING PRESSURE SWITCH (PSPS)

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: idle speed/throttle stop adjustment, binding throttle shaft/linkage or cruise control linkage.

1. Code 52 Displayed. Turn key off and wait 10 seconds. Disconnect PSPS. Install a jumper wire between PSPS circuit and signal return at harness. Repeat KEY ON/ENGINE OFF SELF-TEST. If code 52 is not displayed, replace PSPS and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 52 is still displayed, go to next step.
2. Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and measure resistance between test pin 46 and signal return at PSPS connector. Also measure resistance between test pin 3 (pin No. 24 on 2.3L HSC CFI, 3.0L EFI Car, 4.9L/5.0L EFI Truck) and PSPS circuit at connector. If both readings are less than 5 ohms, replace ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are more than 5 ohms, repair open in circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
3. Connect tachometer and start engine, allowing it to idle in Park or Neutral. Disconnect PSPS circuit at switch. If RPM increases, replace PSPS. If RPM does not increase, go to next step.
4. Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 3 and test pin 46. If reading is less than 5 ohms, repair short in harness. If reading is more than 5 ohms, replace ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Be sure steering wheel was turned 1/2 turn after engine ID code, but before dynamic response code. If not, repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If wheel was turned, go to next step. Be sure wheels are centered.
6. Turn key off, wait 10 seconds. Disconnect PSPS and perform KEY ON/ENGINE OFF SELF-TEST. If code 52 is present, go to step 8). If not, go to next step.
7. Turn key off, wait 10 seconds. Remove harness from 60 pin connector and check for damaged pins or loose wires. Service as necessary. Disconnect PSPS and ECA. Install breakout box. Set DVOM on 200,000-ohm scale. Measure resistance between pins No. 46 and 24 at breakout box. If resistance reading is 10,000 ohms or less service PSPS short and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance reading is not 10,000 ohms or less replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
8. Turn key off, wait 10 seconds. Install breakout box with ECA and PSPS connected. Set DVOM on 200-ohm scale. Turn key on and measure resistance from test pins No. 24 to 46. Start engine. If resistance is less than 10 ohms between KEY ON/ENGINE OFF and engine running, go to next step. If more, go to step 11).
9. Install breakout box, ECA and PSPS. Set DVOM on 200-ohm scale. With engine idling, measure resistance from test pins No. 24 to 46. Turn steering wheel 1/2 turn and return to center. If resistance changes from less than 10 ohms to infinity (indicating PSPS opening), then returns to 10 ohms or less when steering wheel is returned to center position, PSPS system is okay. If not, go to next step.
10. At this point there are only 2 possible causes for the original code 52 engine running: PSPS switch that will not open. Low available hydraulic pressure. Turn key off, wait 10 seconds. Substitute original PSPS with a known good unit. Run ENGINE RUNNING SELF-TEST, turning steering 1/2 turn during test. If code 52 is still present, power steering system is emitting high pressure. If code 52 is not present, PSPS switch is bad.

Power Steering Pressure Switch (PSPS) Circuit. Scheme 59

TEST Q - 5.0L EFI FUEL CONTROL

Note. See HOW TO USE CIRCUIT TESTS before performing this test. Fuel contaminated engine oil may affect service codes 41 and 42. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST . If problem is corrected, change engine oil and filter.

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault: ignition coil, distributor cap, distributor rotor, fouled spark plugs, spark plug wires, PCV valves, EGR valve, air filter, poor ground, fuel pressure, manifold leaks and engine not at operating temperature.

1. Fuel Pressure Check. Turn key off, wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure should be 28-38 psi (1.9-2.6 kg/cm 2 ). If engine will not start or run, turn key on and off several times to increase fuel pressure. If fuel pressure is at 35-45 psi (2.4-3.1 kg/cm 2 ), go to next step. If not, fuel pump and/or fuel pressure regulator problem is indicated.
2. Turn key on. If fuel remains at 35-45 psi (2.4-3.1 kg/cm 2 ) for one minute or longer after key off, go to next step. If not, go to step 7).
3. Turn key off. Install fuel pressure gauge. Pressurize fuel system as outlined in step 1). Disconnect fuel pump inertia switch. Crank engine for 5 seconds. Conduct pressure reading. If pressure is about 10-20 psi (.69-1.4 kg/cm 2 ). EEC system is not fault of no start. If complaint was runs rough, misses, fuel code, or pressure is greater or less than specified, go to next step.
4. Turn key off, wait 10 seconds. Disconnect ECA 60-pin connector and inspect for damage. Service as necessary. Connect breakout box to harness. Leave ECA disconnected. Set DVOM at 200-ohm scale. Measure resistance of injector bank No. 1 between pins No. 37 and 58 at breakout box and record reading. Measure resistance of injector bank No. 2 between test pin No. 37 and 59 at breakout box and record reading. Both readings should be within 3.5-5.0 ohms. If so, go to step 6). If not, go to next step.
5. Turn key off, breakout box installed. Leave ECA disconnected. Set DVOM on 200-ohm scale. Remove all injectors on bank which is suspected of fault. Measure resistance of each injector by connecting one at a time and reading resistance between pins No. 37 and 58 for bank No. 1. Read resistance between pins No. 37 and 59 for bank No. 2. If readings are not between 15-19 ohms, service the harness/connectors on suspect injector. Replace injector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are okay, go to next step.
6. Turn key off, breakout box installed. Connect ECA to breakout box. Connect test lamp between test pins No. 37 and 58 at breakout box. Crank or start engine. Repeat test between pins No. 37 and 59. If no light on one or both test, verify there is 12 volt power at pins No. 37 and 57. Replace connector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If bright lights on one or both tests, check circuit banks No. 1 and 2 for shorts to ground. If okay, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If dim light on both tests, go to next step.
7. Connect tachometer to engine. Run engine at idle. Remove and connect injectors one at a time and note RPM drop. Each injector should produce a 100 RPM momentary drop. ISC will attempt to reestablish RPM. If not, replace faulty injector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If okay, problem is with area common to all cylinders: vacuum/air leak, EGR, etc.
8. Turn key off, wait 10 seconds. Disconnect vehicle harness at EGO sensor. Set DVOM on 20-volt scale. Turn key on. Measure voltage between EGO signal and ground at HEGO harness connector. Voltage should be less than .5 volts. If okay, go to next step. If not, repair short to key power in EGO circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
9. Turn key off, disconnect HEGO. Set DVOM on 200,000-ohm scale. Measure resistance between key power input and EGO circuit at HEGO sensor. If reading is 10,000 ohms or less, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, go to next step.
10. Turn key off, wait 10 seconds. Disconnect vehicle harness at EGO sensor. Ground EGO circuit at EGO sensor vehicle harness connector to engine block. Repeat ENGINE RUNNING SELF-TEST. If code 41 is present, remove ground and go to next step. If not, remove ground and disconnect ECA connector. Inspect for damage. If okay, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
11. Check MAP Sensor. NOTE: Because of MAP sensor influence on fuel control, there is a possibility code 42 could be a result of a MAP problem even though code 22 is not present. The following 2 pinpoint tests will verify proper vacuum to MAP. Turn key off, wait 10 seconds. Disconnect vacuum line from MAP sensor. Install vacuum pump to MAP sensor. Apply 18 in. Hg vacuum to MAP sensor. If sensor holds vacuum, go to next step. If not, replace MAP sensor and connect vacuum line to MAP. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
12. Install vacuum gauge in intake manifold at MAP sensor. Start engine and note vacuum reading. Turn key off, wait 10 seconds. Remove vacuum gauge and "T" and reconnect vacuum line to MAP. Install vacuum gauge in a different source of manifold vacuum. Start engine and note reading. If vacuum readings differ more than 1 in. Hg, inspect vacuum lines for leaks or holes. Service as necessary. If lines are okay, go to next step.
13. EGO Check. Set DVOM on 20-volt scale. With EGO sensor disconnected from harness, connect a DVOM from EGO sensor to engine ground. Disconnect PCV hose. Start engine and run at about 2000 RPM. DVOM should read less than .4 volts within 30 seconds. If so, EGO is okay, go to step 1). If not, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
14. Run vehicle at 2000 RPM for 2 minutes. Turn key off, wait 10 seconds. Perform ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 41 is present, go to next step. If not, go to step 20).
15. Turn key off. Set DVOM on 20-volt scale. Disconnect HEGO sensor from harness. Connect DVOM to HEGO sensor and engine ground. Disconnect and plug vacuum line to MAP sensor. Apply 10 in. Hg vacuum to MAP sensor. Start engine and run at about 2000 RPM. DVOM should read greater than .5 volts within 5 minutes. If so, go to net step. If not, replace HEGO sensor. Reconnect MAP vacuum line and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
16. Turn key off. Install breakout box. Disconnect ECA. Measure resistance between pin No. 49 and engine block ground and between HEGO circuit at HEGO vehicle harness connector and pin No. 29. If both circuits are less than 5 ohms, go to next step. If not, service circuit with greater than 5 ohms resistance. Reconnect MAP vacuum line and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
17. Turn key off. Disconnect EGO and ECA. Install breakout box. Set DVOM to 200,000-ohms range. Measure resistance between test pin No. 29 and 40 at breakout box. If resistance is greater than 20,000 ohms or more, go to next step. If not, correct cause of resistance to ground. Reconnect MAP sensor vacuum line. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
18. Turn key off. Disconnect HEGO. Set DVOM on 200,000-ohm scale. Measure resistance from power ground to HEGO signal at HEGO sensor. If reading is 10,000 ohms or less, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, go to next step.
19. Turn key off, connect ECA. Reconnect HEGO sensor. Be sure MAP vacuum line is disconnected and plugged. Apply 10 in. Hg vacuum to MAP sensor. Start engine and run at about 2000 RPM for one minute. Allow engine to return to idle. Perform ENGINE RUNNING SELF-TEST. If code 41 is present, inspect for corrosion or damaged pins. Reconnect vacuum line and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, HEGO input circuit is okay. Go to step 1).
20. Turn key off. Set DVOM on 200-ohm scale. Disconnect HEGO. Measure resistance between run circuit and ground at heated EGO. Hot-to-warm resistance specification is 5-20 ohms. If okay, go to next step. If not replace HEGO sensor.
21. Turn key on, engine off. Set DVOM on 20-volt scale. Connect positive lead to run circuit and negative lead to ground at HEGO vehicle harness connector. If voltage reading is 10.5 or greater, HEGO is okay. Go to step 1). If not go to next step.
22. Turn key off, wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance of power ground circuit from HEGO vehicle harness connector to battery ground. If resistance is 5 ohms or less, service open in run circuit. If resistance is 5 ohms or more, service open in power ground circuit.
23. Code 41 Continuous Testing. Code 41 indicates that EGO circuit has not switched during closed loop fuel control. It does not necessarily indicate a lean condition. Areas to check include: Vacuum circuits. EGO fuel fouled. Ignition system. Improper fuel. Fuel pressure. If drive concern is still present, repeat steps 3) and 7) only.

5.0L Fuel Control Circuit. Scheme 60

TEST R - 2.3L EFI FUEL CONTROL

Note. See HOW TO USE CIRCUIT TESTS before performing this test. Fuel contaminated engine oil may affect service codes 41 and 42. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST . If problem is corrected, change engine oil and filter.

1. Turn key off and wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure must be 25-35 psi (1.8-2.5 kg/cm 2 ). If engine will not run, cycle key from off to on several times to build up fuel pressure. If fuel pressure is outside range, check electric fuel pump and fuel pressure regulator. If fuel pressure is correct, go to next step.
2. With pressure gauge installed, cycle key from off to on several times to pressurize system. Pressure must remain at 35-45 psi (2.5-3.2 kg/cm 2 ) for 60 seconds after key is turned off. If pressure is not maintained, go to step 7). If pressure is maintained, go to next step.
3. With pressure gauge installed, cycle key from off to on several times to pressurize system. Disconnect fuel pump relay. Crank engine for 5 seconds and take pressure reading immediately after cranking. If pressure reading is 10-20 psi (0.7-1.4 kg/cm 2 ) after cranking, EEC-IV system is NOT at fault for no start. If problem is rough running, missing, fuel code, or if pressure is incorrect after cranking, go to next step. NOTE: Make sure that fuel is of good quality and not contaminated by air or water, as pressure readings may be incorrect with bad or contaminated fuel. Also, pressure drop will be greater when engine is cold than when engine is warm. If coolant is 200°F (93°C) pressure should drop approximately 10 psi (0.7 kg/cm 2 ) in 5 seconds while a pressure drop of 20 psi (1.4 kg/cm 2 ) should occur in 5 seconds with engine coolant at 60°F (15.6°C).
4. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pins 37 and 58 for injector bank 1. Measure resistance between test pins 37 and 59 for injector bank 2. If both readings are between 7.0 and 9.5 ohms, go to step 6). If both readings are not between 7.0 and 9.5 ohms, go to next step.
5. With key off, breakout box installed and ECA disconnected, set DVOM on 200-ohm scale. Disconnect all injectors on suspect bank. Connect each injector individually and test resistance between test pins 37 and 58 for bank 1 or between test pins 37 and 59 for bank 2. If all readings are not between 15.0 and 19.0 ohms, check harness and connectors on injector for shorted or open circuits. If circuits are okay, replace injector(s) and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are between 15.0 and 19.0 ohms, go to next step.
6. With key off, breakout box installed and ECA connected, connect all injectors. Connect non-powered 12-volt test lamp between test pins 37 and 58. Crank or start engine. Repeat procedure with test lamp between test pins 37 and 59. If test lamp does not light on one or both tests, check for 12 volts at test pins 37 and 57. If test pins 37 and 57 have 12 volts, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If test lamp is bright on one or both tests, check circuits to banks 1 and 2 for short to ground. If no short is found, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If test lamp glows dimly on both tests, go to next step.
7. Connect tachometer and run engine at idle. Disconnect and reconnect one injector at a time. Note RPM drop for each injector. If each injector does not produce at least 100 RPM drop when disconnected, replace faulty injector(s) and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If RPM drop is correct for all injectors, problem is in an area common to all cylinders such as vacuum leaks, fuel contamination, EGR, etc. Fuel delivery is okay.
8. Code 42 Displayed. This code indicates an always rich condition. Turn key off and wait 10 seconds. Disconnect vehicle harness at EGO sensor. Set DVOM on 20-volt scale. Turn key on. Measure voltage between HEGO signal and ground at HEGO connector. If voltage is less than .5 volts, service short to power in HEGO circuit. If voltage reading is more than .5 volt, go to next step.
9. Turn key off and disconnect HEGO. Set DVOM on 200,000-ohm scale. Measure resistance from key power input to HEGO circuit at the HEGO. If resistance is 10,000 ohms or less, replace HEGO and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, go to next step.
10. Turn key off and wait 10 seconds. Disconnect vehicle harness at HEGO sensor. These non-EEC areas can cause a code 42: Engine oil contaminated with fuel. Misfire caused by ignition. CANP malfunction. Disconnect vehicle harness at HEGO sensor. Ground HEGO circuit at HEGO sensor vehicle harness connector to engine block. Repeat ENGINE RUNNING SELF-TEST. If code 41 is not present, remove jumper and disconnect ECA and inspect pins for damage or corrosion. If okay, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 41 is present, go to next step.
11. Turn key off, wait 10 seconds. Remove vacuum line from MAP sensor and install vacuum pump. Apply 18 in. Hg vacuum to MAP sensor. If MAP sensor does not hold vacuum, replace MAP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If it does hold vacuum, go to next step.
12. Install vacuum gauge at MAP sensor and at manifold source. Start and run engine. Compare vacuum readings between MAP sensor and engine manifold. If readings are not the same, inspect vacuum lines for leaks, holes or blockage. If readings are the same, go to next step.
13. HEGO Check. Set DVOM on 20-volt scale. With HEGO sensor disconnected from harness, connect a DVOM from HEGO sensor to engine ground. Disconnect PCV hose. Start engine and run at about 2000 RPM. If DVOM reads more than .4 volts within one minute, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If DVOM reads less than .4 volts, HEGO sensor is okay. Repeat step 1).
14. Code 41 Verification. Run vehicle at 2000 RPM for 2 minutes. Turn key off, wait 10 seconds. Perform ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 41 is not present, go to step 20). If code 41 is present, go to next step.
15. With key off, set DVOM on 20-volt scale. Remove HEGO sensor from vehicle harness. Connect DVOM to HEGO sensor and engine ground. Apply 14 in. Hg vacuum to MAP. Start engine and run at approximately 2000 RPM. If DVOM does not read greater than .5 volts within one minute, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If DVOM does read greater, go to next step.
16. Turn key off. Install breakout box and disconnect ECA. Measure resistance between pin No.49 at breakout box and engine block ground and between HEGO circuit at HEGO vehicle harness connector and test pin No. 29 at breakout box. If both readings are more than 5 ohms, fix circuit with greater than 5 ohms resistance and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are less than 5 ohms, go to next step.
17. Turn key off. Disconnect HEGO. Install breakout box and disconnect ECA. Set DVOM to 200,000-ohm scale. Measure resistance between pins No. 29 and 40 at breakout box. If resistance is 10,000 ohms or less, fix cause of resistance to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance is 10,000 ohms or greater, go to next step.
18. Turn key off. Disconnect HEGO and set DVOM on 200,000-ohm scale. Measure resistance from ground to HEGO signal at HEGO sensor. If resistance is 10,000 ohms or less, replace HEGO and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 or more, go to next step.
19. Turn key off. Reconnect HEGO sensor. Apply 14 in. Hg vacuum to MAP sensor. Start engine and run at about 2000 RPM for one minute. Allow engine to return to idle. Perform ENGINE RUNNING SELF-TEST. If code 41 is present, inspect wiring for corrosion or damage. If code 41 is not present, HEGO is okay. Go to step 1).
20. Turn key off. Set DVOM on 200-ohm scale. Disconnect HEGO. Measure resistance between run circuit and ground at HEGO sensor. At room temperature, resistance specification is 2-5 ohms. Hot-to-warm resistance is 5 to 20 ohms. If resistance is not within specification, replace HEGO sensor. If okay, go to next step.
21. Turn key on, engine off. Set DVOM on 20-volt scale. Connect positive lead to run circuit and negative lead to ground at HEGO vehicle harness connector. If voltage reading is 10.5 volts or greater, HEGO system is okay. Go to step 1). If reading was not 10.5 volts or greater, go to next step.
22. Turn key off, wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance of ground circuit from HEGO vehicle harness connector to battery ground. If resistance is less than 5.0 ohms, service open in run circuit. If more than 5.0 ohms, service open ground circuit.

2.3L EFI Fuel Control Circuits. Scheme 61

TEST S - 2.9L, 3.0L & 4.9L EFI FUEL CONTROL

Note. See HOW TO USE CIRCUIT TESTS before performing this test. Fuel contaminated engine oil may affect service codes 41 and 42. If this is suspected, remove PCV valve from valve cover and repeat QUICK TEST . If problem is corrected, change engine oil and filter.

1. Turn key off and wait 10 seconds. Install fuel pressure gauge. Start and run engine. Fuel pressure must be 35-45 psi (2.46-3.16 kg/cm 2 ) for 2.9L and 3.0L engines, 50-60 psi (3.45-4.14 kg/cm 2 ) for 4.9L engines. Fuel pressure with engine on must be 28-38 psi (1.90-262 kg/cm 2 ) for 2.9L and 3.0L engines, 42-52 psi (2.90-3.59 kg/cm 2 ) for 4.9L engines. If engine will not start, cycle the key off and on a few times to build up fuel pressure. If fuel pressure is outside range, check electric fuel pump and fuel pressure regulator. If fuel pressure is correct, go to next step.
2. Turn key on. If fuel pressure cannot hold specification for one minute, go to step 7). If fuel pressure is okay, go to next step.
3. Fuel Delivery Test. Turn key off. Install fuel pressure gauge. Pressurize fuel system as in step 1). Disconnect fuel pump inertia switch. Crank engine for 5 seconds, then take pressure reading. If pressure drops approximately 5-8 psi (.34-.55 kg/cm 2 ) at end of crank cycle, EEC system is not at fault. If pressure does not drop, or complaint was car runs rough or misses, go to next step. NOTE: Make sure that fuel is of good quality and not contaminated by air or water, as pressure readings may be incorrect with bad or contaminated fuel. Also, pressure drop will be greater when engine is cold than when engine is warm. If coolant is 200°F (93°C) pressure should drop approximately 10 psi (0.7 kg/cm 2 ) in 5 seconds while a pressure drop of 20 psi (1.4 kg/cm 2 ) should occur in 5 seconds with engine coolant at 60°F (15.6°C).
4. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for damaged pins, corrosion or loose wires. Connect breakout box, leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance of injector bank one between test pins No. 37 and 58 at breakout box. Measure resistance of injector bank 2 between test pins No. 37 and 59 at breakout box. If both readings are between 5.0 and 6.5 ohms, go to step 6). If not go to next step.
5. Turn key off, breakout box installed. Leave ECA disconnected. Set DVOM on 200-ohm scale. Disconnect all injectors on suspect bank. Measure resistance of each injector by connecting one injector at a time. Read resistance between test pins No. 37 and 58 for bank 1, or test pins No. 37 and 59 for bank 2. If readings are not between 16-18 ohms, service harness and connectors on injector for possible opens or shorts. If okay, replace injector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are between 16-18 ohms, go to next step.
6. Turn key off, breakout box installed. Connect ECA to breakout box. Connect test lamp between pins No. 37 and 58 at breakout box. Crank or start engine. Repeat test between pins No. 37 and 59 at breakout box. No. light on one or both tests indicates ECA needs replacing if there is 12 volt battery power at pins No. 37 and 57. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If bright light on one or more tests, check banks 1 and 2 for shorts to ground. If okay, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If dim lights glow on both tests, go to next step.
7. Connect tachometer to engine and run at idle. Disconnect and reconnect injectors one at a time. Note RPM drop for each injector. Each injector should produce a 100 RPM drop. The ISC will attempt to re-establish RPM. If not, replace defective injector and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If system works properly, fuel delivery is okay. Check for possible vacuum leak.
8. Turn key off, wait 10 seconds. Disconnect vehicle harness at HEGO sensor. Set DVOM on 20-volt scale. Turn key on. Measure voltage between EGO signal and power ground at HEGO harness connector. If voltage is more than .5 volts, repair short to power in EGO circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If voltage is less, go to next step.
9. Turn key off, disconnect HEGO sensor. Set DVOM on 200,000-ohm scale. Measure resistance between key power input to EGO circuit at HEGO sensor. If reading is 10,000 ohms or less, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, go to next step.
10. Turn key off, wait 10 seconds. These non-EEC areas can cause a code 42: Engine oil contaminated with fuel. Misfire caused by ignition. CANP malfunction. Disconnect vehicle harness at EGO sensor. Jump (ground) EGO circuit at EGO sensor vehicle harness connector to engine block. Repeat ENGINE RUNNING SELF-TEST. If code 41 is produced, remove jumper and go to next step. If not, remove jumper and disconnect ECA. Inspect for damage or corrosion. If okay, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
11. MAP Sensor Test. Turn key off, wait 10 seconds. Remove vacuum line from MAP sensor and install vacuum pump. Apply 18 in. Hg vacuum to MAP sensor. If sensor does not hold vacuum, replace MAP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If MAP sensor does hold vacuum, go to next step.
12. Using "T", install vacuum gauge in intake manifold vacuum line at MAP sensor. Start engine, note vacuum reading. Turn key off, wait 10 seconds. Remove vacuum gauge and "T" and reconnect vacuum line to MAP. Install "T" to different source of manifold vacuum. Start engine and note reading. If vacuum readings were different by more than 1 in. Hg, check vacuum lines for leaks and service as necessary. If not, go to next step.
13. Set DVOM on 20-volt scale. With EGO sensor disconnected from harness, connect DVOM from EGO sensor to engine ground. Remove PCV hose. Start engine and run at about 2000 RPM. If DVOM reads less than .4 volts within 30 seconds, EGO sensor is okay, repeat step 1). If DVOM reads more than .4 volts within 30 seconds, replace EGO and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
14. Run engine at 2000 RPM for 2 minutes. Turn key off, wait 10 seconds. Do ENGINE RUNNING «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 41 is still present, go to next step. If not, to step 20).
15. Turn key off, set DVOM on 20-volt scale. Remove HEGO sensor from vehicle harness. NOTE: Following vacuum/air leaks in non-EEC areas could cause a code 41: Leaking vacuum actuator. Engine sealing. EGR system. PCV system. HEGO sensor contaminated with lead. Connect DVOM to HEGO sensor and engine ground. Plug vacuum line to MAP sensor. Apply 10 in. Hg vacuum to MAP sensor. Start engine and run about 2000 RPM. If DVOM does not read more than .5 volts within one minute, replace HEGO sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If DVOM does read more than .5 volts within one minute, go to next step.
16. Turn key off, install breakout box. Disconnect ECA. Measure resistance between pin No. 49 at breakout box and engine block ground and between HEGO circuit at HEGO harness connector and test pin No. 29 at breakout box. If both circuits are less than 5 ohms, service as necessary circuit with greater than 5 ohms resistance. Reconnect MAP vacuum and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both circuits are less than 5 ohms, go to next step.
17. Turn key off, EGO disconnected, breakout box installed. Disconnect ECA. Set DVOM to 200,000-ohms scale. Measure resistance between pins No. 29 and 40 at breakout box. If resistance is less than 10,000 ohms, correct cause. Reconnect MAP and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance is 10,000 ohms or more, go to next step.
18. Turn key off. Disconnect HEGO and set DVOM on 200,000-ohm scale. Measure resistance from power ground to HEGO signal at HEGO sensor. If reading is 10,000 ohms or less, replace HEGO sensor, reconnect MAP line and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, go to next step.
19. Turn key off. Connect ECA and HEGO sensor. Disconnect and plug MAP vacuum line. Apply 10 in. Hg vacuum to MAP sensor. Start engine and run at about 2000 RPM for one minute. Let engine return to idle. Perform ENGINE RUNNING SELF-TEST. If code 41 is present, inspect pins for corrosion or damage. Reconnect MAP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 41 is not present, reconnect MAP vacuum line. Go to step 1).
20. Turn key off. Set DVOM on 200-ohm scale. Disconnect HEGO sensor. Measure resistance between run circuit and power ground at heated EGO sensor. Hot-to-warm resistance is 5-20 ohms. Room temperature resistance is 2-5 ohms. If not within specifications, replace HEGO sensor. If specifications are okay, go to next step.
21. Turn key on, engine off, set DVOM on 20-volt scale. Connect positive lead to run circuit and negative lead to ground at HEGO harness. If voltage reading is 10.5 volts or greater, HEGO system is okay. Reconnect HEGO and go to step 1). If reading is not 10.5 volts or more, go to next step.
22. Turn key off, wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance of power ground circuit from HEGO harness connector to battery ground. If resistance is 5.0 ohms or less, service short in run circuit. If reading is more than 5.0 ohms, service open in ground circuit.
23. Code 41 CONTINUOUS Testing. Code 41 indicates the EGO circuit has not switched during closed loop fuel control. Code 41 does not necessarily indicate a lean condition. Closed Loop: fuel control under influences of EGO sensor. Open Loop: fuel control NOT under influence of EGO sensor. Using fuel control service code, determine cause of fuel control problem. Areas to check are: Vacuum Circuits: check vacuum leaks, PCV system, engine sealing. EGO Fuel Fouled: When an over-rich condition has been found to exist, make a thorough check of the ignition system. EGO contamination can be burned-off by driving vehicle at sustained high speeds followed by a few hard accelerations. Ignition System: always in default spark (10 degrees). See «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . Improper Fueling: lead fouled EGO sensor. Fuel Pressure: repeat steps 1 and 2). If condition still exists, perform steps 3) and 7) only.

2.9L, 3.0L & 4.9L EFI Fuel Control Circuits. Scheme 62

TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: fuel lines, fuel filters, throttle body, fuel pump or contaminated fuel.

1. Install fuel pressure gauge. Check if fuel pump runs. Cycle key from off to on several times. DO NOT crank engine. Pump should operate each time key is on. If pump runs as indicated, check electric fuel pump system for problems. If pump does not run as indicated, go to next step.
2. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Turn key on, leaving engine off. Set DVOM on 20 volt scale. Measure voltage between test pin 37 and 40, and between test pin 57 and 60. If either reading is less than 10.5 volts, go to «TEST B - VEHICLE BATTERY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-b-vehicle-battery) , step 1). If both readings are 10.5 volts or more, go to next step.
3. Turn key off and wait 10 seconds. Leave breakout box installed and ECA connected. Locate and disconnect fuel pump inertia switch. Set DVOM on 200-ohm scale and measure switch resistance. If reading is 5 ohms or more, replace inertia switch and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
4. Turn key on, leaving engine off. Leave breakout box installed and ECA connected. Locate fuel pump relay. Set DVOM on 20 volt scale. Measure voltage between chassis ground and power-to pump(s) circuit at fuel pump relay while cranking engine. If reading is less than 8 volts, go to step 6). If reading is 8 volts or more, go to next step.
5. Turn key on, leaving engine off. Leave breakout box installed and ECA connected. Locate fuel pump(s). Set DVOM on 20-volt scale. Measure voltage between chassis ground and power-to-pump(s) circuit at fuel pump(s) while cranking. If reading is 8 volts or more, service electric fuel pump(s). If reading is less than 8 volts, repair open in power-to-pump(s) circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
6. Turn key on, leaving engine off. Leave breakout box installed and ECA connected. Locate fuel pump relay. Set DVOM on 20 volt scale. Measure voltage between chassis ground and V BATT circuit at fuel pump relay. If reading is less than 10.5 volts, repair open in V BATT circuit between fuel pump relay and battery positive post. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or more, go to next step.
7. Turn key on, leaving engine off. Leave breakout box installed and ECA connected. Locate fuel pump relay. Set DVOM on 20 volt scale. Measure voltage between chassis ground and V POWER circuit at fuel pump relay. If reading is less than 10.5 volts, repair open in V POWER circuit between fuel pump relay and ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or more, go to next step.
8. Turn key off and wait 10 seconds. Leave breakout box installed and ECA connected. With DVOM on 200-ohm scale, measure resistance between fuel pump circuit at pump relay and test pin 22. If reading is 5 ohms or more, repair open in fuel pump circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
9. Turn key off. Leave breakout box installed and disconnect ECA. Disconnect fuel pump relay. With DVOM on 200,000-ohm scale, measure resistance between test pin 22, 40 and 60. If reading is less than 10,000 ohms, repair short in fuel pump circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, go to next step.
10. Turn key off and wait 10 seconds. Leave breakout box installed. Leave fuel pump relay and ECA disconnected. With DVOM on 200,000-ohm scale, measure resistance between test pin 22, 37 and 57. If reading is less than 10,000 ohms, repair short to power in fuel pump circuit. Connect ECA and attempt to start engine. If engine does not start, replace ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, connect fuel pump relay and go to next step.
11. Leave breakout box installed and ECA disconnected. Install a jumper wire between test pin 22 and either test pin 40 or 60. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between chassis ground and power-to-pump(s) circuit at fuel pump relay. If reading is 10.5 volts or more, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 10.5 volts, replace fuel pump relay. Connect ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
12. Turn key off. Remove fuel pump relay. If fuel pump turns off, replace fuel pump relay. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If fuel pump does not turn off, repair short to power-to-pump(s) circuit.

Fuel Pump (Inertia Switch) Circuits. Scheme 63

TEST U - EGR ON/OFF CHECK

Note. Code 34 may be result of high volume exhaust vent system reducing backpressure. If this is suspected, perform test in well-ventilated area without exhaust vent connected.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: air or vacuum leaks, EGR flow restrictions or EGR value.

1. Code 34 Displayed. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect negative DVOM lead to STO at SELF-TEST connector and positive lead to positive battery terminal. Insert jumper wire between STI and signal return circuit at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads zero volts). Depress and release throttle and observe DVOM reading. If DVOM did not show high voltage, depress throttle to WOT and release. If output voltage does not go too high, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 15). Leave test equipment hooked up. If DVOM registered high reading, stay in OUTPUT STATE CHECK and go to next step.
2. Set DVOM on 20-volt scale. Connect DVOM positive lead to VPWR circuit at EGR solenoid and negative lead to EGR output circuit. Depress and release throttle several times to cycle EGR solenoid output on and off. If output does not cycle on and off, remove jumper wire and go to step 5). If output cycles on and off, go to next step.
3. Connect vacuum pump to solenoid vacuum supply port and vacuum gauge to output port of solenoid. Apply minimum vacuum of 6 in. Hg. Depress and release throttle several times to cycle EGR solenoid output while maintaining vacuum at supply port. Note gauge reading. If vacuum output does not cycle, replace EGR solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum output cycles, go to next step.
4. With vacuum lines disconnected at EGR solenoid, start engine. If vacuum is present, EEC-IV system is not cause of problem. Check exhaust gas recirculation system. If vacuum is not present, correct vacuum source blockage or leak and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Turn key off and wait 10 seconds. Disconnect EGR solenoid. Set DVOM on 200-ohm scale and measure solenoid resistance. If reading is less than 65 ohms or more than 110 ohms, replace solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance is between 65 and 110 ohms, connect solenoid and go to next step.
6. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage at EGR solenoid connector between VPWR circuit and ground. If reading is less than 10.5 volts, repair open in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or higher, go to next step.
7. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 35 and EGR circuit at connector. If reading is 5 ohms or higher, repair open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
8. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect EGR solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 35, 40, 46, and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If any reading is 10,000 ohms or more, go to next step.
9. Turn key off and wait 10 seconds. Leave breakout box installed with ECA and EGR solenoid disconnected. With DVOM on 200,000-ohm scale, measure resistance between test pin 35, 37 and 57. If any reading is less than 10,000 ohms, repair short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is still repeated, replace ECA. If any reading is 10,000 ohms or more, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

EGR ON/OFF Circuit. Scheme 64

TEST V - AIR MANAGEMENT SYSTEM

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: thermactor air system drive belt, air pump or valve.

1. Codes 44 (94), 45 (95) & 46 (96) Displayed. Ensure correct vacuum line routing to TAB/TAD solenoids and by-pass diverter valve. Use vehicle emissions label as a guide. Check for kinked or blocked vacuum lines. Check for kinked or blocked air hoses. Check for disconnected vacuum lines. If problems are detected, correct hose routing, repair faults and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If hoses are good and code 44 (94) is displayed, go to step 4). If code 46 (96) is displayed, go to step 3). If code 45 (95) is displayed, go to next step.
2. Code 45 (95) Displayed. This test applies to TAD equipped models only. Disconnect and plug vacuum line at diverter valve. Turn key off and wait 10 seconds. Repeat ENGINE RUNNING SELF-TEST and record codes. If code 45 (95) is displayed, EEC-IV system is okay. Check diverter valve and/or check valve for problem. If code 45 (95) is not displayed, go to step 4).
3. Code 46 (96) Displayed. This test applies to TAB equipped models only. Disconnect and plug vacuum line at by-pass valve. Turn key off and wait 10 seconds. Repeat ENGINE RUNNING SELF-TEST and record codes. If code 46 (96) is displayed, EEC-IV system is okay. Check by-pass valve for problem. If code 46 (96) is not displayed, go to next step.
4. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. With DVOM on 20-volt scale, connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to battery positive terminal. Using a jumper wire, connect STI circuit to signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads zero volts). Depress and release throttle. DVOM should change to a high voltage reading. If reading did not change, depress throttle to WOT and release. If STO voltage does not go high, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 15). Leave test equipment hooked up. If reading changed, remain in OUTPUT STATE CHECK and go to next step.
5. Set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR circuit and negative test lead to TAB circuit at TAB solenoid. While observing DVOM, depress and release throttle several times to cycle output on and off. Repeat for TAD solenoid. Connect positive test lead to VPWR circuit and negative test lead to TAD circuit at TAD solenoid. Cycle output on and off. If either solenoid does not cycle on and off, remove jumper and go to step 8). If both solenoids cycle on and off, go to next step.
6. Connect vacuum pump to TAB solenoid vacuum supply port. Connect vacuum gauge to output port. Maintain vacuum at source while depressing and releasing throttle to cycle output on and off. Observe vacuum gauge. Repeat for TAD solenoid. If either vacuum output does not cycle on and off, replace solenoid assembly and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both vacuum outputs cycle on and off, go to next step.
7. With vacuum lines disconnected at TAB/TAD solenoid assembly, start engine and check for vacuum. If vacuum is present, EEC-IV system is okay. Check thermactor valve and air pump for problem. If no vacuum is present, repair blockage and/or leaks as required and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
8. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect TAB and TAD solenoid connectors. Measure resistance of both solenoids. If either reading is less than 50 ohms or more than 100 ohms, replace TAB/TAD solenoid assembly and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are between 50 and 100 ohms, connect TAB and TAD solenoids. Go to next step.
9. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between TAB solenoid VPWR circuit and battery ground. Repeat for TAD solenoid. If either voltage reading is less than 10.5 volts, repair open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are higher than 10.5 volts, go to next step.
10. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin 51 and TAB circuit at harness connector. Measure resistance between test pin 11 and TAD circuit at harness connector. If either reading is 5 ohms or higher, repair harness open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are less than 5 ohms, go to next step.
11. Turn key off and wait 10 seconds. Set DVOM on 200,000-ohm scale. Leave breakout box installed and ECA disconnected. Disconnect TAB and TAD solenoid, and measure resistance between test pins 51 and/or 11 and test pins 37 and 57. If any reading is less than 10,000 ohms, repair short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If any reading is 10,000 ohms or more, go to next step.
12. Turn key off and wait 10 seconds. Set DVOM on 200,000-ohm scale. Leave breakout box installed and ECA disconnected. Disconnect TAB and TAD solenoid, and measure resistance between test pins 51 and/or 11 and test pins 40, 46 and 60. If any reading is less than 10,000 ohms, repair circuit short to ground. Remove breakout box, connect harness to ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA. If any reading is 10,000 ohms or more, replace ECA. Remove breakout box, connect harness to ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Air Management Circuits. Scheme 65

TEST W - CANISTER PURGE (CANP) CHECK

1. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to positive battery terminal. Using a jumper wire, connect STI circuit to signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads zero volts). Depress and release throttle, DVOM should change to a high voltage reading. If reading did not change, depress throttle to WOT and release. If STO voltage does not go high, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 15). Leave test equipment hooked up. If reading changed, remain in OUTPUT STATE CHECK and go to next step.
2. Set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR on CANP solenoid and negative test lead to CANP output circuit on solenoid. Depress and release throttle several times to cycle solenoid on and off. If CANP solenoid does not cycle, remove jumper wire and go to step 6). If CANP solenoid does cycle, go to next step.
3. Turn key off. Disconnect CANP solenoid. Remove vacuum hose at canister purge solenoid on PCV side. Apply 16 in. Hg to CANP solenoid. If CANP solenoid does not hold vacuum for 20 seconds, replace CANP solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If CANP solenoid does hold vacuum, leave vacuum pump in place and go to next step.
4. Turn CANP circuit off. Reconnect CANP solenoid connector. Apply 16 in. Hg vacuum to CANP solenoid as in step 3). Depress and release throttle. If vacuum is not released, replace CANP solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vacuum is released, remove jumper from STI to signal return and go to next step.
5. Disconnect vacuum hose at canister purge solenoid at PCV side. Start engine. If vacuum is present at engine vacuum hose, EEC-IV system is okay. If no vacuum is present, check vacuum line for proper routing or kinks.
6. Turn key off, wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect CANP solenoid connector and measure solenoid resistance. If resistance is not between 40-90 ohms, replace CANP and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance is within range, go to next step.
7. Turn key on, engine off. Set DVOM on 20-volt scale. Measure voltage between VPWR at CANP solenoid vehicle harness connector and battery ground. If voltage reading is 10.5 volts or less, service harness open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 or greater, go to next step.
8. Turn key off, wait 10 seconds. Remove ECA and inspect both 60-pin connectors for damaged pins, corrosion, or loose wires. Connect breakout box to harness. Leave ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between pin No. 31 at breakout box and CANP on vehicle harness connector. If resistance is less than 5 ohms, go to next step. If not, service open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
9. Turn key off, wait 10 seconds. Leave breakout box to harness. Leave ECA disconnected. Disconnect CANP solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between pins No. 31, 40, 46 and 60 at breakout box. If resistance readings are 10,000 or less service short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are more, go to next step.
10. Turn key off, wait 10 seconds. Set DVOM on 200,000-ohm scale. Leave breakout box installed with ECA and CANP solenoid disconnected. Measure resistance between pins No. 31, 37 and 57 at breakout box. If both readings are 10,000 ohms or more, remove breakout box and replace ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If readings are 10,000 ohms or less, service short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Canister Purge (CANP) Circuit. Scheme 66

TEST X - IDLE SPEED CONTROL (BY-PASS AIR)

Note. If engine is running rough or has rough idle, correct before running test. Causes may be in ignition system, fuel system or EGR system.

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: engine not up to operating temperature, engine over operating temperature, improper idle speed/throttle stop adjustment or cruise control linkage.

1. Turn key off. Connect engine tachometer and start engine. Disconnect Idle Speed Control (ISC) harness. If RPM drops or if engine stalls, go to next step. If not, go to step 3).
2. If EGR service codes 31, 32, 33 or 34 are displayed, go to ENGINE RUNNING SELF-TEST table and perform appropriate test. If not, service next code. If codes 12 or 13 are displayed, go to next step.
3. If service codes 22, 41, 42, 91 or 92 are displayed, go to ENGINE RUNNING SELF-TEST table and perform appropriate test. If not, go to next step.
4. With key off set DVOM on 200-ohm scale. Disconnect ISC solenoid connector and measure solenoid resistance. If resistance is between 7-13 ohms, go to next step. If not, replace ISC solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. With key off and ISC harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance from either ISC pin to ISC solenoid housing. If reading is 10,000 ohms or greater, go to next step. If reading is less than 10,000 ohms, replace ISC solenoid. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
6. Leave ISC harness disconnected. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between VPWR circuit at ISC harness and battery ground terminal. If reading is less than 10.5 volts, repair open in circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or more, go to next step.
7. Turn key off and wait 10 seconds. Leave ISC harness disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. With DVOM on 200-ohm scale, measure resistance between test pin 21 and ISC circuit at ISC harness connector. If reading is 5 ohms or more, repair open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
8. Turn key off and wait 10 seconds. Leave ISC harness disconnected. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 21 and test pins 40, 46, and 60. If all readings are less than 10,000 ohms, repair short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If any reading is 10,000 ohms or more, go to next step.
9. Turn key off and wait 10 seconds. Leave breakout box installed. Leave ECA and ISC solenoid disconnected. With DVOM on 200,000-ohm scale, measure resistance between test pin 21 and 37. If reading is less than 10,000 ohms, repair short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10,000 ohms or more, go to next step.
10. With key off, connect ECA and ISC. Leave breakout box installed. With vehicle prepared for «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) , set DVOM on 20-volt scale. Connect DVOM between test pin 21 and 40. Start engine. Slowly increase and decrease RPM. Observe DVOM. Does the DVOM vary? If so, then go to the next step. If not, replace processor and run «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
11. Verify curb idle is within specification. If it is, replace ISC actuator and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, check engine vacuum hoses. Be sure throttle plates are closed and linkage is not binding. If all is okay, replace ISC and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
12. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Start and run engine at 2000 RPM for 2 minutes, until inlet radiator hose is hot and pressurized. Turn key and wait 10 seconds. Perform ENGINE RUNNING SELF-TEST. If code 17 is still displayed, inspect throttle body and air inlet for contamination. Service as necessary. If okay, adjust curb idle speed and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 17 is not displayed, service other codes as necessary.
13. Code 13 Displayed. Turn key off and connect tachometer. Start engine. Disconnect ISC harness connector. If RPM drops or engine stalls, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, check engine vacuum hoses, linkage, or speed control for binding. If okay, replace ISC and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
14. Code 48 Displayed. Repair any holes, cracks or disconnections to air cleaner outlet tube (between van airflow meter and fuel charging assembly.) Perform ENGINE RUNNING SELF-TEST. If code 48 is present, check for other source of unmetered airflow. If not, EEC system is okay for metered air.

Idle Speed Control (By-Pass Air) Circuit. Scheme 67

TEST BB - SHIFT INDICATOR LIGHT (SIL)

1. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Put transmission in Neutral. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to positive battery terminal. Install a jumper wire between STI and signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of CONTINUOUS SELF-TEST codes (DVOM reads zero volts). Depress and release throttle while watching DVOM reading. If reading did not change to a high voltage, depress throttle to WOT position and release. If STO voltage does not go to high reading, go to step 7). Leave test equipment hooked up. If reading changes to high voltage, remain in OUTPUT STATE CHECK and go to next step.
2. If truck is equipped with 4.9L EFI engine, go directly to step 5). On all others, set DVOM on 20-volt scale. Connect DVOM positive test lead to battery positive terminal and negative test lead to pin 1 on dimmer relay. Depress and release throttle several times to cycle relay on and off. If relay does not cycle, go to step 5). If relay cycles, go to next step.
3. Set DVOM on 20-volt scale. Connect DVOM positive test lead to battery positive terminal and negative test lead to pin 2 on dimmer relay. Depress and release throttle several times to cycle relay on and off. If relay does not cycle, remove jumper wire and replace dimmer relay. If relay does cycle, remove jumper wire and go to next step.
4. Turn key off and wait 10 seconds. With DVOM set to 200-ohm scale, measure resistance between pin 2 of dimmer relay and SIL bulb. If reading is less than 5 ohms, replace SIL bulb. If reading is 5 ohms or more, repair open circuit in harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. Set DVOM on 20-volt scale. Connect DVOM positive test lead to battery positive terminal and negative test lead to SIL circuit of top gear switch. Depress and release throttle several times to cycle SIL circuit on and off. If truck uses a 4.9L EFI engine and SIL circuit cycles, change SIL bulb. If SIL circuit cycles on all others, repair open circuit in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If SIL circuit does not cycle (all models), go to next step.
6. Set DVOM on 20-volt scale. Connect DVOM positive test lead to positive battery terminal and negative test lead to STO circuit of top gear switch. Depress and release throttle several times to cycle STO circuit on and off. If STO circuit cycles, replace top gear switch. If STO does not cycle, repair open circuit in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
7. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Put transmission in top gear. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to positive battery terminal. Install a jumper wire between STI and signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads zero volts). Depress and release throttle while watching DVOM reading. If reading changed to high voltage, check SIL bulb and fuse No. 15. If bulb and fuse are good, repair short to ground in SIL circuit. If reading did not change to high voltage, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not) , step 15).

Shift Indicator Light (SIL) Circuits. Scheme 68

Scheme 69

1. Use only VOM/DVOM, not STAR tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to positive battery terminal. Install a jumper wire between STI and signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF SELF-TEST until end of «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) codes (DVOM reads zero volts). Depress and release throttle while watching DVOM reading. If reading did not change to a high voltage, depress throttle to WOT position and release. If STO voltage does not go to high reading, go to «TEST HH - NO CODES/CODES NOT LISTED»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-hh-no-codescodes-not), step 15). Leave test equipment hooked up. If reading changes to high voltage, remain in OUTPUT STATE CHECK and go to next step.
2. Turn key on, leaving engine off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA to box. Place A/C switch on A/C position and set DVOM on 20-volt scale. Connect DVOM positive test lead to test pin 37 and negative test lead to test pin 54. Depress and release throttle several times while watching DVOM. If A/C clutch output cycles, EEC-IV system is okay. Check A/C system operation. If A/C clutch output does not cycle, remove jumper wire and go to next step.
3. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect WAC relay and measure relay resistance. If reading is less than 50 ohms or more than 70 ohms, replace WAC relay and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is between 50 and 70 ohms, connect WAC relay and go to next step.
4. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR circuit and negative test lead to ground. Measure VPWR voltage at WAC relay. If reading is less than 10.5 volts, repair open in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is 10.5 volts or more, go to next step. (Scheme 69): WOT A/C Cut-Out Circuits for 2.3L & 2.9L EFI Models
5. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 54 and WAC circuit at relay connector. If reading is 5 ohms or more, repair open in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is less than 5 ohms, go to next step.
6. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 54 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If all readings are 10,000 ohms or more, go to next step.
7. Turn key off and wait 10 seconds. Leave breakout box installed, ECA disconnected, and DVOM on 200,000-ohm scale. Disconnect WAC solenoid. Measure resistance between test pin 54 and test pins 37 and 57. If reading is 10,000 ohms or more, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading is less than 10,000 ohms, repair short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test).
8. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between test pin 10 and 40. If reading fluctuates from 4.0 to 10.5 volts as A/C switch is cycled, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If reading does not fluctuate, go to next step.
9. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Measure resistance between ACC test pin 10 and A/C clutch. On 2.3L OHC/EFI engine equipped trucks, also measure resistance between test pin 24 (ACD) and A/C demand switch. If any reading is 5 ohms or more, repair harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test). If all readings are less than 5 ohms, EEC-IV is okay. Check A/C system.

WOT A/C Cut-Out Circuits for 3.0L EFI Models. Scheme 70

TEST DD - CONVERTER CLUTCH OVERRIDE CCO

1. Turn key off and wait 10 seconds. Set DVOM on 200-ohm scale. Disconnect CCO solenoid connector and measure solenoid resistance. If reading is less than 26 ohms or higher than 40 ohms, replace CCO solenoid and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is between 26 and 40 ohms, connect solenoid and go to next step.
2. Turn key on, leaving engine off. With DVOM on 20-volt scale, measure voltage at CCO solenoid connector between VPWR circuit and ground. If reading is 10.5 volts or less, repair open circuit in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10.5 volts or higher, go to next step.
3. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 53 and CCO circuit at solenoid harness connector. If reading is 5 ohms or higher, repair open circuit in harness and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
4. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect CCO solenoid. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 55 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 10,000 ohms or higher, go to next step.
5. Turn key off and wait 10 seconds. Leave breakout box installed, ECA and CCO solenoid disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 55 and test pins 37 and 57. If all readings are 10,000 ohms or higher, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If any reading is less than 10,000 ohms, repair short to power and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code is repeated, replace ECA.

CCO Circuit. Scheme 71

TEST EE - DYNAMIC RESPONSE TEST

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: person testing EEC-IV system did not perform brief wide open throttle (WOT) after Dynamic Response code, mechanical engine problems, or engine did not go over 2000 RPM.

Code 77 Displayed. Repeat ENGINE RUNNING SELF-TEST. With SELF-TEST activated, restart engine. Code 2 (20 on STAR tester) indicates start of test. After Dynamic Response code 1 (10 on STAR tester) is displayed, perform brief WOT. Dynamic Response service codes will be displayed. If code 77 is still present, replace ECA and repeat QUICK TEST . If code 77 is not displayed, DYNAMIC RESPONSE TEST passed. Service other codes (if displayed) as required.

TEST FF - IGNITION DIAGNOSTIC MONITOR (IDM)

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: ignition module, ignition coil, spark plugs and/or high tension cables, distributor and PIP sensor.

1. Turn key off and wait 10 seconds. Disconnect E-Core ignition connector from coil. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pin 4 and negative terminal on ignition coil. If reading is less than 20,000 ohms or higher than 24,000 ohms, repair open circuit and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is between 20,000 and 24,000 ohms, go to next step.
2. Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. With DVOM on 200,000-ohm scale, measure resistance between test pin 4 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short to ground and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are 10,000 ohms or more, go to next step.
3. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for indication of fault while lightly tapping on TFI module and wiggling TFI harness connector. If fault is indicated, disconnect TFI harness. Inspect connector and terminals for damage. If connector and terminals are okay, check TFI ignition system. If no fault is indicated, go to next step.
4. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for indication of fault while wiggling, shaking, or bending small sections of harness while working from TFI connector toward firewall. Repeat process from firewall to ECA. Perform this test to check for faults in the following circuits: IDM CIRCUIT FAULTS Condition Test Pin PIP Open/Shorted to Ground Check circuit at Test Pin 56 SPOUT Shorted to Ground Check circuit at Test Pin 36 Ignition Ground Open Check circuit at Test Pin 16 IDM Open/Shorted to Ground/Power Check circuit at Test Pin 4 Perform «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) on circuits one at a time in order to isolate fault. If fault is indicated, isolate and repair harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault is indicated, go to next step.
5. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector and terminals for damage. If connector and terminals are damaged, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If connector and terminals are okay, fault cannot be duplicated at this time. IDM testing is complete. Connect ECA.

IDM Circuits. Scheme 72

TEST GG - SPARK TIMING CHECK

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: engine condition (valves, vacuum leaks, valve timing, EGR valve, etc.), PIP sensor, TFI ignition module.

1. Perform ENGINE RUNNING SELF-TEST and verify that SELF-TEST is activated. Check and record timing while in ENGINE RUNNING SELF-TEST. System locks timing then returns to normal 2 minutes after last service code is displayed. If timing is 27-33°, spark timing is correct. Go to ENGINE RUNNING SELF-TEST. If timing is not 27-33°, go to next step.
2. Locate Spark Output (SPOUT) connector and open the connection. Start engine and check for 10° BTDC base timing plus or minus 3°. If base timing is correct, go to next step. If base timing is not correct, adjust base timing. After timing is adjusted, connect SPOUT and perform «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) . See «TIMING CHECK»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__timing-check) in «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) (ALL VEHICLES) section of this article.
3. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box. Turn key on, leaving engine off. With DVOM on 20-volt scale, measure voltage between test pin 37 and 40, and between test pin 57 and 60. If either reading is less than 10.5 volts, go to «TEST B - VEHICLE BATTERY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-b-vehicle-battery) , step 1). If both readings are 10.5 volts or more, go to next step.
4. Turn key off and wait 10 seconds. Disconnect harness connector at TFI module. With DVOM on 200-ohm scale, measure resistance between test pin 36 and pin 2 (SPOUT circuit) at TFI harness connector. If reading is greater than 5 ohms, repair open circuit. Connect SPOUT connector and check timing as described in step 1). If reading is 5 ohms or less, go to next step.
5. Leave breakout box installed and TFI harness disconnected. Turn key off and set DVOM on 200-ohm scale. Measure resistance between test pin 16 and pin 6 (IGN GRAND circuit) at TFI harness connector. If reading is less than 5 ohms, go to «TEST A - NO START»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-a-no-start) , step 7). If reading is 5 ohms or more, repair harness as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

Spark Timing Check Circuit. Scheme 73

TEST HH - NO CODES/CODES NOT LISTED

1. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage between VREF circuit at TPS harness connector and signal return circuit in SELF-TEST connector. If reading is less than 4 volts or more than 6 volts, go to «TEST C - REFERENCE VOLTAGE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-c-reference-voltage) , step 1). If reading is between 4 and 6 volts, connect TPS and go to next step.
2. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 48 and Self-Test Input (STI) at SELF-TEST connector pigtail. If reading is 5 ohms or more, repair open in circuit. If reading is less than 5 ohms, go to next step.
3. With breakout box installed and DVOM on 200-ohm scale, measure resistance between test pin 17 and Self-Test Output (STO) at SELF-TEST connector. If reading is 5 ohms or more, repair open in circuit. If reading is less than 5 ohms, go to next step.
4. Turn key off. With breakout box installed and DVOM on 200 ohm scale, measure resistance between test pin 49 and EGO sensor engine block ground. If reading is 5 ohms or more, repair EGO sensor ground wire or open circuit bad connection. If reading is less than 5 ohms, go to next step.
5. With breakout box installed and DVOM on 200-ohm scale, measure resistance between STO at SELF-TEST connector and engine block ground. If reading is more than 5 ohms, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is less than 5 ohms, go to next step.
6. Leave key off and breakout box installed. Set DVOM on 20 volt scale. Connect DVOM between test pin 30 and test pin 40 or 60. Perform ENGINE RUNNING SELF-TEST. If reading is greater than 1 volt, repair intermittent fault in NDS harness connector or switch. If okay, go to ENGINE RUNNING SELF-TEST for appropriate service codes. If reading is not greater than 1 volt, repair intermittent fault in NDS harness connector or switch. If okay, go to next step.
7. Leave key off and breakout box installed. Set DVOM on 20 volt scale. Connect DVOM to test pin 37 or 57 and test pin 40 or 60. Turn key on, then off. Wait 10 seconds. If reading does not changes from 10.5 volts (or higher) to zero volts, replace EEC power relay. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading changes from 10.5 volts (or higher) to zero volts, go to next step.
8. If vehicle is not equipped with shift indicator light, repair Self-Test Output (STO) circuit for short to ground. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If vehicle is equipped with shift indicator light, go «TEST BB - SHIFT INDICATOR LIGHT (SIL)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-bb-shift-indicator-light) , step 7).
9. CONTINUOUS Code 15 Displayed. Clear continuous memory codes using procedure described in «CONTINUOUS SELF-TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-self-test) . Repeat KEY ON/ENGINE OFF SELF-TEST through continuous memory code output. If continuous code 15 is not displayed, continuous code 15 testing is complete. If continuous code 15 is displayed, go to next step. NOTE: Continuous code 15 is displayed when power to Keep Alive Memory (KAM), test pin 1 at ECA is interrupted. Code 15 may also be displayed the first time SELF-TEST is performed and power is restored to ECA. Repeat SELF-TEST to ensure correct diagnosis.
10. Ensure that EEC-IV components and wiring are not close to high tension secondary voltage wires or ignition components. If EEC-IV wiring is close to high tension wires, reroute EEC-IV wiring and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If continuous code 15 is no longer displayed, continuous code 15 testing is complete. If continuous code 15 is still displayed, go to next step.
11. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Connect DVOM positive test lead to test pin 1 and negative test lead to pin 40 or 60. Turn key on and observe voltage reading. If reading is less than 10 volts, repair open to KAM circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 10 volts or greater, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
12. Check or perform diagnosis of non-EEC related areas. Check all areas that may contribute to a particular condition in order of probability, ease of accomplishment, and accessibility. Use your technical knowledge and experience to determine which areas may be the source of problem before starting a more involved diagnosis. After correcting faults, go to next step.
13. Turn key off and wait 10 seconds. Perform KEY ON/ENGINE OFF SELF-TEST. Leave key on to enter OUTPUT STATE TEST. If codes 23, 53, 63 or 68 were present, go to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) , step 3). If code 11 was present, go to next step. If no code was present, go to step 1).
14. Check throttle and throttle linkage for sticking and binding. If okay, replace TP sensor and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If not, service as necessary.
15. Power To ECA Check. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box. Turn key on, leaving engine off. Set DVOM on 20-volt scale. Measure voltage between test pin 37 and 40, and between test pin 57 and 60. If either reading is less than 10.5 volts, go to «TEST B - VEHICLE BATTERY»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-b-vehicle-battery) , step 1). If both readings are 10.5 volts or more, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
16. turn key off. Check that EEC-IV wiring and components are greater than 2 inches from secondary ignition wires and ignition coil and 4 inches from distributor, coil tower, starter motor and wiring. If all conditions are okay, go to next step. If not, service as necessary and rerun «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
17. Turn key off and install breakout box. Leave ECA disconnected and inspect for damaged pins. Set DVOM on 200-ohm scale. Measure resistance between pin No. 20 at box and chassis ground. If resistance is less than 5 ohms, go to next step. If not, service harness as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

No Codes/Codes Not Listed Circuits. Scheme 74

TEST II - SYSTEM CHECK

1. ISC Check. Attempt to start engine at part throttle. If engine runs only at part throttle, go to «TEST X - IDLE SPEED CONTROL (BY-PASS AIR)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-x-idle-speed-control) , step 3). If engine does not run, go to next step.
2. MAP Check. Turn key off and disconnect MAP sensor. Connect MAP tester between harness and MAP sensor. Connect banana plugs of tester into DVOM and set DVOM on 20-volt scale. Turn key on and measure sensor voltage output while cranking engine. If DVOM reading does not decrease from specified range, go to «TEST G - MAP/BP SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-g-mapbp-sensor) , step 13). On 3.0L EFI engine, if DVOM reading decreases from specified range, go to «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 1). On all other engines, if DVOM reading decreases from specified range, go to next step. MAP VOLTAGE OUTPUT Elevation (Ft.) Voltage Output (Volts) 0 1.55-1.63 1000 1.52-1.60 2000 1.49-1.57 3000 1.46-1.54 4000 1.43-1.51 5000 1.40-1.48 6000 1.37-1.45 7000 1.35-1.43
3. EGR Check. Disconnect and plug vacuum hose at EGR valve. Ensure that EGR valve is closed. Attempt to start vehicle. If vehicle runs, go to: «TEST E - EVP»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-e-evp-egrc) , EGRC & EGRV, step 8) for all 2.3L models. «TEST I - THROTTLE POSITION SENSOR (TPS)»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-i-throttle-position-sensor) , step 22) for 4.9L & 5.0L models.

On 2.9L engines, check exhaust gas recirculation system. If vehicle does not run, go to

1. «TEST R - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-r-23l-efi-fuel) .3L EFI FUEL CONTROL, step 1) for 2.3L models.
2. «TEST S - 2»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-s-29l-30l) .9L, 3.0L & 4.9L EFI FUEL CONTROL, step 1) for 2.9L, 3.0L & 4.9L models.
3. «TEST Q - 5»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-q-50l-efi-fuel) .0L EFI FUEL CONTROL, step 1) for 5.0L models.

TEST JJ - ERRATIC IGNITION

1. Code 14 Displayed. This code indicates that 2 successive erratic Profile Ignition Pick-Up (PIP) pulses were sent to ECA, causing possible engine miss or stall. Check EEC-IV and TFI ignition system for loose wires and connections, arcing secondary ignition components (coil, cap, wires, etc.), or an on-board 2-way radio. Make sure radio antenna and power leads are routed properly. If any of the above conditions are present, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If none are present, go to next step.
2. Turn key off and wait 10 seconds. Deactivate SELF-TEST. Using «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for indication of fault while lightly tapping on TFI ignition module and distributor, and while wiggling TFI harness connector. If fault is indicated, disconnect and inspect connectors and terminals. If connectors and terminals are okay, diagnose TFI ignition system. If no fault is indicated, go to next step.
3. While in «CONTINUOUS MONITOR (WIGGLE) TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__continuous-monitor-wiggle-test) , observe VOM or STAR tester LED for fault while wiggling, shaking, or bending small sections of harness from TFI module to firewall. Also check harness from firewall to ECA. Isolate PIP circuit, if required. If fault is indicated, isolate and repair problem. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If no fault indicated, go to next step.
4. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector and terminals for damage. If connector and terminals are okay, fault cannot be duplicated at this time. Diagnose TFI ignition system. If connector and terminals are damaged, repair as necessary and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .

TEST KK - AXOD TRANSAXLE

Note. Perform this test only when KEY ON/ENGINE OFF SELF-TEST service codes 62, 67 and 89 are present; when ENGINE RUNNING SELF-TEST service code 62 is displayed; or when CONTINUOUS SELF-TEST service codes 29, 39, 57, 59 and 69 are displayed. Ensure that all components are connected before performing test. Perform TEST KK - AXOD TRANSAXLE on a slight upgrade or flat terrain.

AXOD Drive Cycle Test.

Record and zero service codes. Warm engine to operating temperature. With transaxle in "D" range, lightly accelerate from a stop to 40 MPH to allow transaxle to shift into 3rd gear. Hold speed and throttle opening steady for a minimum of 15 seconds (30 seconds above 4000 feet altitude).

Shift transaxle into overdrive and accelerate lightly from 40 to 50 MPH to allow transaxle to shift into 4th gear. Hold speed and throttle opening steady for a minimum of 15 seconds.

With transaxle in 4th gear, throttle open and speed steady, lightly apply and release brakes (enough to light brake lamps). Hold speed and throttle opening steady for an additional 15 seconds minimum.

Brake to a stop and remain stopped for a minimum of 20 seconds with transaxle in overdrive. Perform QUICK TEST and record service.

1. CONTINUOUS Code 29 Displayed. Perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) and return to this step. If continuous code 29 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is complete. If continuous code 29 is displayed, go to next step.
2. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and Vehicle Speed Sensor (VSS) disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 3 and VSS + circuit at harness connector. Measure resistance between test pin No. 6 and VSS - Circuit at harness connector. If both readings are 5 ohms or more, repair open(s) in VSS harness, then repeat step 1). If both readings are 5 ohms or less, go to next step.
3. With key off, ECA and VSS disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 3 and test pins No. 37, 40 and 6. Then measure resistance between test pins No. 6, 37 and 40. If all readings are less than 1000 ohms, repair short(s) in VSS harness, then repeat step 1). If all readings are more than 1000 ohms, go to next step.
4. Substitute original VSS with a good known VSS. With ECA and VSS connected, perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) and return to this step. If continuous code 29 is displayed, replace ECA then repeat step 1). If continuous code 29 is not displayed, replace original VSS then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
5. CONTINUOUS Code 69 Displayed. Perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) and return to this step. If continuous code 69 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is complete. If continuous code 69 is displayed, go to next step.
6. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 19 and THS 3/2 circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in THS 3/2 circuit then repeat step 5). If reading is 5 ohms or less, go to next step.
7. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pins No. 19 and 37. If reading is less than 10,000 ohms, repair short to power in THS 3/2 circuit, then repeat step 5). If reading is more than 10,000 ohms, go to next step.
8. With key off and breakout box installed, connect ECA and AXOD harness. Install a jumper wire between test pins No. 19 and 40. Perform KEY ON/ENGINE OFF SELF-TEST. If code 62 is displayed problem is transaxle related. If code 62 is not displayed, remove jumper wire, replace ECA, and then repeat step 5).
9. CONTINUOUS Code 59 Displayed. Perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) and return to this step. If continuous code 59 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is complete. If continuous code 59 is displayed, go to next step.
10. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 18 and THS 4/3 circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in THS 4/3 harness, then repeat step 9). If reading is 5 ohms or less, go to next step.
11. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance between pins No. 18 and 37. If reading is less than 10,000 ohms, repair short to power in THS 4/3 circuit, then repeat step 9). If reading is higher than 10,000 ohms, go to next step.
12. With key off and breakout box installed, connect ECA and AXOD harness. Install a jumper wire between test pins No. 18 and 40. Perform KEY ON/ENGINE OFF SELF-TEST. If code 62 is displayed, remove jumper wire and go to AXOD TRANSAXLE ELECTRICAL SYSTEM DIAGNOSIS. If code 62 is not displayed, remove jumper wire, replace ECA, and then repeat step 9).
13. Continuous Code 39 Displayed. Perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) then return to this step. If continuous code 59 is also present, go directly to step 9). If continuous code 39 is displayed, problem is transaxle related. If continuous code 39 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is completed.
14. Continuous Code 57 Displayed. Perform «TEST KK - AXOD TRANSAXLE»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-kk-axod-transaxle) then return to this step. If continuous code 57 is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is completed. If continuous code 57 is displayed, go to next step.
15. Turn key of and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 30 and NPS circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in NPS circuit, then repeat step 14). If reading is 5 ohms or less, problem is transaxle related.
16. Code 89 Displayed. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 37 and VPWR circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in VPWR circuit then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 5 ohms or less, go to next step.
17. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 53 and LUS circuit at AXOD harness connector. If reading is more than 5 ohms, repair open in LUS circuit then repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If reading is 5 ohms or less, go to next step.
18. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 53, 37 and 40. If both readings are less than 10,000 ohms, repair shorts in LUS harness. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 89 is still displayed, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If both readings are higher than 10,000 ohms, go to next step.
19. With key off, breakout box installed, and ECA disconnected, connect AXOD harness. Set DVOM on 200,000-ohm scale. Measure resistance between test pins No. 53 and 57. If resistance is between 20 and 40 ohms, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If resistance is not between 20 and 40 ohms, problem is transaxle related.
20. Cod 62 Displayed. Perform ENGINE RUNNING SELF-TEST and record codes. If code 62 is displayed, fault is in THS 4/3 circuit. Go to next step. If code 62 is not displayed, fault is in THS 3/2 circuit. Go to next step.
21. Turn key off and disconnect AXOD harness. Perform KEY ON/ENGINE OFF SELF-TEST. If code 62 is not displayed, problem is transaxle related. If code 62 is displayed, go to next step.
22. Turn key off, install breakout box, leaving ECA and AXOD harness disconnected. Set DVOM on 200,000-ohm scale. Measure resistance between test pins No. 18, 40 and 60. Also measure resistance between test pin No. 19 and test pins No. 40 and 60. If all readings are less than 10,000 ohms, repair short(s) to ground. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are higher than 10,000 ohms, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) .
23. Verify that code 62 is present in ENGINE RUNNING SELF-TEST. If code 62 is displayed, problem is transaxle related. If code is not displayed, fault cannot be duplicated at this time. If any other codes are present, return to «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) for instructions. If none, test is complete.
24. Code 67 Displayed. Turn key on, leaving engine off. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA to box. Set DVOM on 20 volt scale. Measure voltage between test pin 30 and 46. If reading is more than 4.0 volts, go to «TEST M - NEUTRAL A/C SWITCH»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) , step 4). If reading is less than 4.0 volts, go to next step.
25. With key off, breakout box installed, and ECA and AXOD harness disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pins No. 30, 40 and 60. If all readings are less than 10,000 ohms, repair short to ground in NPS circuit. Repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If all readings are higher than 10,000 ohms, go to next step.
26. With key off and breakout box installed, connect ECA. Leave AXOD harness disconnected. Perform KEY ON/ENGINE OFF SELF-TEST. If code 67 is displayed, replace ECA and repeat «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . If code 67 is not displayed, problem is transaxle related.
27. Turn key off, wait 10 seconds. Disconnect Vehicle Speed Sensor (VSS). Set DVOM on 2000-ohm scale. Measure resistance across VSS. If resistance between 190-230 ohms, go to next step. If not, replace sensor.
28. Turn key off, wait 10 seconds. Disconnect ECA 60-pin connector. Inspect pins for corrosion or damage. Install breakout box. Disconnect ECA and VSS. Set DVOM on 200-ohm scale. Measure resistance between pins No. 3, 6 and VSS. If both resistances are 5 ohms or less, go to next step. If not, service open in VSS harness.
29. Turn key off. Disconnect ECA and VSS. Set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 3 and test pins No. 37, 40 and 6. Then measure resistance between test pin No. 6 and test pins No. 37 and 40. If all readings are more than 1000 ohms, go to next step. If not, repair short in VSS harness.
30. Substitute VSS with known good sensor. Disconnect ECA and VSS. Test drive vehicle. If drive complaint eliminated, replace VSS. If not, replace ECA.

AXOD Transaxle Circuits. Scheme 75

INTERMITTENT NO START, QUITS ON ROAD WITH NO RESTART

1. If engine does not start, do «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) diagnostic procedure.
2. If engine starts, check for operating fuel pump when ignition is on, spark at coil, ignition system (wires, cap and rotor), Thick Film Integrated (TFI) ignition module and baseline key voltages with breakout box.

INTERMITTENT SURGING AT STEADY SPEED

1. Check plug firing voltages, cylinder balance, base ignition timing, spark plug type and MAP and BP sensor (depending on vehicle). See «MAP/BP SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table at end of article.
2. On Vane Airflow Meter (VAF) equipped vehicles, check for unmetered air leaks. On all vehicles, check flow of fuel injectors and fuel pressure.

INTERMITTENT QUITS ON ROAD & RESTARTS

Check baseline readings of key voltages while engine is operating. Compare voltages with readings obtained when intermittent problem occurs and perform QUICK TEST .

INTERMITTENT BUCKING & JERKING

1. Check ignition system secondary wires, distributor cap and rotor, Thick Film Integrated (TFI) ignition module, engine spark, plug firing voltages, cylinder balance, and base ignition timing. Check spark plugs for fouling and proper gap.
2. Perform «QUICK TEST»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__quick-test) . Connect Manifold Absolute Pressure (MAP)/Barometric Pressure (BP) tester to MAP or BP sensor (depending on vehicle). Check readings with engine off and with ignition switch in "ON" position. Compare reading with «MAP/BP SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table at end of article.
3. On Vane Airflow Meter (VAF) equipped vehicles, check for unmetered air leaks. Check for loose air tubes, missing hoses, or vacuum plugs.

INTERMITTENT ERRATIC RUNNING, ROUGH IDLE

1. Check color at top of fuel injectors to ensure correct application. Check distributor cap, plug firing voltages, cylinder balance, and base ignition timing.
2. Check spark plugs for fouling and proper gap, cylinder compression, engine/valve train operation. Check Thick Film Integrated (TFI) ignition module, Profile Ignition Pick-Up (PIP), and coil.
3. Check Spark Output (SPOUT) connector. Connect Manifold Absolute Pressure (MAP)/Barometric Pressure (BS) tester to MAP or BP sensor (depending on vehicle). Check readings with engine off and with ignition switch in "ON" position. Compare reading with «MAP/BP SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing) table at end of article.
4. Repeat MAP test with engine running. Reading should decrease at idle and increase when throttle is opened. On MAP sensor equipped vehicles, if readings with engine off and ignition on do not match values given, go to «TEST H - KNOCK SENSOR»(/ford/bronco-ii/i-1984-1990/remont/testing-diagnostics/#cec-diagnosing-testing__test-h-knock-sensor) , MANIFOLD ABSOLUTE PRESSURE (MAP)/BAROMETRIC PRESSURE (BP) SENSOR test.
5. If MAP sensor does not change when throttle is opened (engine running), substitute a known good vacuum hose at sensor and repeat test. On vehicles equipped with either MAP or BP sensors, substitute sensor(s) and retest.
6. On Vane Airflow Meter (VAF) equipped vehicles, check for unmetered air leaks. Using breakout box, monitor VAF signal while manually moving van door. Voltage must smoothly increase as door is opened.
7. Using Fuel Injector Tester/Cleaner (Rotunda 113-00001), check flow of injectors.

MAP/BP SPECIFICATIONS

Aerostar 2.3L EFI EEC-IV Wiring Diagram. Scheme 76

Bronco II & Ranger 2.3L EFI EEC-IV Wiring Diagram. Scheme 77

Bronco II & Ranger 2.9L EFI EEC-IV Wiring Diagram. Scheme 78

Aerostar 3.0L EFI EEC-IV Wiring Diagram. Scheme 79

"E" Series 4.9L EFI EEC-IV Wiring Diagram. Scheme 80

Bronco & "F" Series 4.9L EFI EEC-IV Wiring Diagram. Scheme 81

"E" Series 5.0L EFI EEC-IV Wiring Diagram. Scheme 82

Bronco & "F" Series 5.0L EFI EEC-IV Wiring Diagram. Scheme 83

See also:
• CIRCUIT TESTS
• QUICK TEST
• KEY ON/ENGINE OFF (KOEO)
• KEY ON/ENGINE RUNNING (KOER)
• EQUIPMENT HOOK-UP
• TEST A - NO START
• DIAGNOSIS BY SYMPTOM TEST
• CONTINUOUS MONITOR (WIGGLE) TEST
• PREPARATION
• TIMING CHECK
• CONTINUOUS SELF-TEST
• TEST HH - NO CODES/CODES NOT LISTED
• TEST GG - SPARK TIMING CHECK
• TEST II - SYSTEM CHECK
• TEST G - MAP/BP SENSOR
• TEST X - IDLE SPEED CONTROL (BY-PASS AIR)
• TEST H - KNOCK SENSOR
• TEST BB - SHIFT INDICATOR LIGHT (SIL)
• TEST R - 2
• TEST P - POWER STEERING PRESSURE SWITCH (PSPS)
• TEST T - FUEL PUMP CIRCUIT (INERTIA SWITCH)
• TEST S - 2
• TEST KK - AXOD TRANSAXLE
• TEST C - REFERENCE VOLTAGE
• TEST B - VEHICLE BATTERY
• HOW TO USE CIRCUIT TESTS
• TEST E - EVP
• TEST I - THROTTLE POSITION SENSOR (TPS)
• TEST Q - 5