5.0l/5.7l Vins [f,8] Pfi "c" Charts Chevrolet Camaro III рестайлинг

MODEL IDENTIFICATION

Note. The following conditions must be met before testing: Engine at operating temperature, Engine in closed loop operation, Engine idling ("Engine Run" column), Test terminal NOT grounded, and Scanner or ALDL tool NOT installed.

Repair procedures in this article are sometimes identified by a specific body code. The following table lists GM division, model name, and body types that apply to the body codes.

MODEL IDENTIFICATION

DESCRIPTION

The computerized engine control system monitors as many as 19 engine/vehicle functions. (Scheme 262) This system controls engine operation and lowers exhaust emissions while maintaining fuel economy and driveability. The Electronic Control Module (ECM) is the "brain" of the CCC system.

The computerized engine control system is primarily an emission control system, designed to maintain a 14.7:1 air/fuel ratio under all operating conditions. When the ideal air/fuel ratio is maintained, the 3-way catalytic converter can control Oxides of Nitrogen (NOx), Hydrocarbon (HC) and Carbon Monoxide (CO) emissions.

ECM Conditions Sensed & Systems Controlled. Scheme 262

DIAGNOSTIC SYSTEM OPERATION

The ECM of computerized engine control system is equipped with a self-diagnostic system which detects system failures or abnormalities. As a bulb and system check, "SERVICE ENGINE SOON" light will glow when ignition switch is turned to "ON" position and engine is not running. When engine is started, light should go out. If not, a malfunction has been detected in the computerized engine control system or "SERVICE ENGINE SOON" light circuit is faulty.

When a malfunction occurs, ECM will illuminate the "SERVICE ENGINE SOON" light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code will be stored in ECM memory. Malfunctions are recorded as "hard failures" or as "intermittent failures".

"HARD FAILURES"

Hard failures cause "SERVICE ENGINE SOON" light to glow and remain on until the malfunction is repaired. If light comes on and remains on during vehicle operation, cause of malfunction must be determined using diagnostic charts. If a sensor fails, ECM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is driveable, but loss of good driveability will most likely be encountered.

"INTERMITTENT FAILURES"

Intermittent failures cause "SERVICE ENGINE SOON" light to flicker or illuminate and go out about 10 seconds after the intermittent fault goes away. The corresponding trouble code, however, will be retained in ECM memory. If related fault does not reoccur within 50 engine restarts, related trouble code will be erased from ECM memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in the CEC TESTS W/O CODES article in this section.

Note. Trouble codes will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds. Others may require operation for 5 minutes or longer under engine load. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.

BASIC DIAGNOSTIC PROCEDURE

Note. Most computerized engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, ignition high tension wires, fuel supply, electrical connections and vacuum hoses should be checked. Failure to do so may result in lost diagnostic time.

Diagnosis of the computerized engine control system should be performed in the following order

1. Make sure that all engine systems not related to the computer system are operating properly. Do not proceed with testing unless all other problems have been repaired.
2. Perform appropriate DIAGNOSTIC CIRCUIT CHECK for that system. If trouble codes were displayed (other than Code 12), decide whether codes are "hard" or "intermittent" trouble codes. "Hard" codes will cause the "SERVICE ENGINE SOON" light to illuminate continuously while engine is running. See ECM TROUBLE CODE DEFINITIONS table in the CEC PFI TESTS/CODES article in this section.
3. If no trouble codes were displayed, perform FIELD SERVICE MODE CHECK procedures.
4. If no trouble is indicated by the FIELD SERVICE MODE check and/or a driveability problem exists, refer to SYMPTOM DIAGNOSIS TROUBLE SHOOTING procedures in the CEC TESTS W/O CODES article in this section or SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMATERS in this article. The comments there will send you to the proper component charts or tell you the most likely system/component to check.
5. After any repairs are made, clear any trouble codes and perform FIELD SERVICE MODE check again.

Scheme 263

1. Turn ignition on. Do not start engine. "SERVICE ENGINE SOON" light should glow. Locate Assembly Line Data Link (ALDL) connector attached to ECM wiring harness under instrument panel, left or right of steering column (under cigar lighter plate in center console on Fiero). Insert jumper wire across terminal "B", "DIAGNOSTIC TERMINAL" and terminal "A", "GROUND". (Scheme 263) CAUTION: Inserting spade lug (jumper lead) into terminals of ALDL connector grounds "DIAGNOSTIC TERMINAL". Do not ground ALDL connector until after ignition is on (engine not running). (Scheme 263): ALDL Connector Terminal Identification NOTE: In some of the diagnostic and trouble shooting charts the Assembly Line Data Link (ALDL) may also be referred to as the Assembly Line Communication Link (ALCL). These are referring to the same connector. It is also the test point for connection of aftermarket "Scan" testers.
2. "SERVICE ENGINE SOON" light should flash Code "12". Code "12" consists of "FLASH", pause, "FLASH", "FLASH" followed by a longer pause. Trouble Code "12" will be repeated 2 more times. If any other trouble codes are stored in ECM memory, they will be displayed in the same manner. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.
3. To exit diagnostic mode, turn ignition off and remove jmper wire from ALDL connector.

DIAGNOSTIC MATERIALS

Note. The charts described in the following paragraphs are arranged later in this article, by engine size and fuel system type.

DIAGNOSTIC CHARTS

The diagnostic charts are used to find and repair problems which the on-car diagnostics have found. These charts include

1. Charts which test the reliability of the self-diagnostic system.
2. Charts which help fix problems which are "SERVICE ENGINE SOON" light related.
3. Charts which test the computerized fuel control system performance.
4. Charts which help fix a problem when the on-car diagnostics don't work.
5. ENGINE CRANKS BUT WON'T RUN charts. Refer to the appropriate TROUBLE SHOOTING chart in the CEC TESTS W/O CODES article in this section.
6. Charts where a stored trouble code leads you to a particular problem. See ECM TROUBLE CODE DEFINITION and DIAGNOSTIC AIDS in this section. Charts which are used because the FIELD SERVICE MODE CHECK found a problem.

Note. Although there are many charts connected with computer diagnosis, only 2 charts are needed to prove system is operating properly. Normally, only 3 charts are necessary to find a problem, if one exists.

DIAGNOSTIC AIDS

Diagnostic aids (located in each "trouble code" chart box for each system) are additional tips used to help diagnose trouble codes when inspected circuit checks out okay. Diagnostic aids may help lead to a definitive solution to that trouble code problem. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section.

FIELD SERVICE MODE CHECK (FUEL INJECTED MODELS)

On fuel injected models, "SERVICE ENGINE SOON" light will indicate operational mode of engine if ALDL is grounded while engine is running. In closed loop mode, "SERVICE ENGINE SOON" light will flash at a rate of one flash per second. In open loop, light will flash at a rate of 2.5 flashes per second. If light is off all or most of the time, a lean exhaust is indicated. If light is on all or most of the time, a rich exhaust is indicated.

This test confirms proper operation of fuel system and verifies closed loop operation. Clear codes and perform this test after any repair is completed. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section. When performing this check, always engage parking brake and block DRIVE wheels. The parking brake on front-wheel drive models does NOT hold the drive wheels.

Note. On some engines, oxygen sensor will cool off after only a short period of time while engine is idling. This will cause engine to go into open loop. To restore closed loop mode, run engine at part throttle several minutes and accelerate from idle to part throttle several times.

SPECIAL DIAGNOSTIC TOOLS

Note. Special "Scan" testers plugged into the ALDL may be used to read trouble codes and check voltages in the system on the serial data line (terminal "E" on EFI and terminal "M" on EFI with P-4 systems). These testers can save a great deal of time. For more information on testing with codes, refer to the CEC PFI TESTS/CODES article in this section. For more information see SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMETERS table in this article.

The computerized engine control system is most easily diagnosed using a "Scan" tester, however, other tools may aid in diagnosing problems if a "Scan" tester is unavailable. These tools are: a tachometer, a dwell meter, test light, ohmmeter, digital voltmeter with 10-megohm impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights (TBI and PFI) and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connector at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic chart.

Note. If engine operation seems to change when dwell meter is connected to Green wire, remove dwell meter and use another type. A few brands are not compatible with computerized engine control system.

When engine is at operating temperature and idling, dwell meter needle should vary between 10-50 degrees. This indicates closed loop operation. Before engine reaches operating temperature, dwell should be fixed between 10-50 degrees, indicating open loop operation. If after reaching normal operating temperature dwell is fixed between 10-50 degrees, less than 10 degrees or more than 50 degrees, refer to CHART A - DWELL FIXED diagnostic chart for that system. Refer to the 5.0L/5.7L VINS [F,8] PFI "A" CHARTS article in this section.

SCAN TESTER USAGE

Note. Prior to connection of scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received by scan tester will be accurate. This is done by performing appropriate DIAGNOSTIC CIRCUIT CHECK for that system. If vehicle does not pass diagnostic circuit check, information received by scan tester may be invalid. CCC Scan tester is a specialized tester which, when plugged into ALDL, can be used to diagnose on-board computer control stems by providing instant access to circuit voltage information without need to crawl under dash or hood to back-probe sensors and connectors.

Scan testers cut down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN TESTER - TEST DATA PARAMETERS table. They also furnish information on output device (solenoids and motors) status. Status parameters, however, are only an indication that output signals have been sent to devices by the ECM. It does not indicate if devices have responded properly to that signal. This will need to be verified at output device using a voltmeter or test light.

Note. Code 12 should always exist when ALDL is grounded with key on and engine not running but may not be indicated by all makes of scan tester.

If trouble codes are not present, this is not an indication that there is not a problem. CCC related problems are about 20 percent codes and 80 percent driveability. Sensors that are out of specification WILL NOT set a trouble code but WILL cause driveability problems. Use of a scan tester is easiest method of checking sensor specifications and other data parameters. Tester is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See the SCAN TESTER - TEST DATA PARAMETERS table below.

Note. Information obtained by scan tester is only as accurate as the tester itself. If erroneous voltage signals are suspected, it will be necessary to verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are in evidence, turn ignition off, remove tester, turn ignition on and ground ALDL "DIAGNOSTIC TERMINAL". If same codes are not flashed by "SERVICE ENGINE SOON" light that were indicated by scan tester, tester cannot be used on vehicle and information obtained by it will not be guaranteed accurate.

SCAN TESTER - TEST DATA PARAMETERS

Note. Information in the following tables is typical readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated every 1 1/4 seconds. On systems using P-4 computers, parameter updates are virtually instantaneous. Not all devices & systems are used on all models.

THROTTLE BODY INJECTION

Note. This ECM voltage chart can be used with a digital voltmeter to help save time in diagnosis. Voltages on the car being tested my vary slightly from these due to battery or alternator charging level.

DIAGNOSTIC CIRCUIT CHECK

The Diagnostic Circuit Check is an organized approach for identifying fuel injection problems using the Assembly Line Data Link (ALDL). This communication link can provide diagnostic information for display on any "Scan" tester designed for this purpose.

If the "Scan" tester is not operating, check tester on another vehicle. If okay, the cigar lighter socket should be checked for 12 volts and a good ground. With the ignition on, if the "Scan" tester reads "NO DATA" or "NO ALDL", check the serial data wire for an open or short to ground. Also check for an open diagnostic "test" terminal "B". Refer to appropriate CHART A1 schematic for circuit wiring reference. With the ignition on, the serial data line should vary between 2-5 volts and the diagnostic line should have about 5 volts present. See the 5.0L/5.7L VINS [F,8] PFI "A" CHARTS article in this section. See SCAN TESTER USAGE and SCAN TESTER - TEST DATA PARAMETERS table in this article.

Diagnostic Circuit Check. Scheme 264

CHART C1A - PARK/NEUTRAL SWITCH

The Park/Neutral switch contacts are a part of the neutral start switch. Contacts are closed to ground in Park or Neutral. The ECM applies and monitors a 12-volt signal on circuit No. 434 and senses a closed switch when voltage drops to less than one volt. If circuit No. 434 indicates Park/Neutral (grounded) while in Drive, the EGR system would be inoperative, resulting in possible detonation. If circuit No. 434 indicates Drive (open), a dip in idle may exist when gear selector is moved to Drive.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Checks for a switch closed to ground in Park.
2. Checks for an open switch in Drive.
3. To test for an intermittent or misadjusted switch in Drive, be sure "Scan" tester indicates Drive, even while wiggling shifter.

Flow Chart - Park/Neutral Switch ("F" Body). Scheme 265

Flow Chart - Park/Neutral Switch ("F" Body). Scheme 266

CHART C2A - INJECTOR BALANCE TEST

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector that has a pressure drop of 1.5 psi (.11 kg/cm 2 ) or more, greater than or less than other injectors, should be considered faulty.

Note. Allow engine to cool down to avoid irregular readings due to "Hot Soak" fuel boiling. In order to prevent flooding, the INJECTOR BALANCE TEST should not be repeated more than once, without starting and running engine.

1. With ignition off, connect Fuel Pressure Gauge (J 34730-1) to pressure tap. Unplug harness connector at all injectors. Connect Injector Tester (J 34730-3) to one of the injectors. On turbocharged engines, use adapter harness supplied with injector tester to pulse injectors that are not accessible.
2. Follow manufacturer's instructions for use of the adapter harness. Ignition should be turned off for at least 10 seconds to complete ECM shutdown cycle.
3. Turn ignition on. Fuel pump should run at least 2 seconds after ignition is turned on. Bleed air from gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Turn ignition off for at least 10 seconds.
4. Turn ignition on again to bring fuel pressure to maximum. Record initial pressure reading. Energize tester one time and note pressure drop at lowest point.
5. Disregard any slight pressure drop after low point is reached. Subtracting second pressure reading from initial reading indicates amount of injector pressure drop.
6. Repeat test step 4) on each injector and compare amount of pressure drop. Recheck injectors that do not read within pressure drop range. Replace injector(s) that fail second check.
7. If injectors are all okay, plug in harness connectors and review SYMPTOMS in TROUBLE SHOOTING section.

Flow Chart - Injector Balance Test. Scheme 267

CHART C2C - IDLE AIR CONTROL ("F" & "Y" BODIES)

The ECM will control engine idle speed by moving the Idle Air Control (IAC) valve to control airflow around the throttle plate. It does this by sending voltage pulses to the proper motor winding for each internal IAC motor. This will cause the motor shaft and valve to move in or out of the motor a given distance for each pulse received. The IAC position is measured in counts. Zero counts is a fully extended valve (no airflow), 255 counts is a fully retracted valve (maximum airflow).

To increase idle speed, the ECM will send a signal to retract the IAC valve and allow more air to flow through the idle air passage and by-pass the throttle plate. This will increase the IAC counts. To decrease idle speed the ECM will send a signal to extend the IAC valve and reduce airflow through the idle air passage around the throttle plate. This will reduce the IAC counts.

Each time the engine is started and then the ignition is turned off, the ECM will reset the IAC valve. This is done by sending enough extend pulses to seat the valve (to zero counts). The fully seated valve is the ECM reference zero. A given number of counts are then calculated by the ECM. This is how the ECM knows what the motor position is for a given idle speed.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Continue with test even if engine will not idle. If idle is too low, "Scan" tester will display 80 or more counts. If idle is high it will display zero counts. Occasionally, an erratic or unstable idle may occur. Engine speed may vary 200 RPM or more up or down. If this condition exists, disconnect IAC motor. If the condition is unchanged, the IAC is not at fault. There is a system problem. Proceed to DIAGNOSTIC AIDS.
2. When the engine was stopped, the IAC valve retracted to a fixed "Park" position for increased airflow and idle speed during the next engine start. A "Scan" tester will display 40 or more counts.
3. Be sure to disconnect the IAC valve prior to this test. The test light will confirm the ECM signals by a steady or flashing light on all circuits.
4. There is a remote possibility that one of the circuits is shorted to voltage which would have been indicated by a steady light. Disconnect ECM and turn the ignition on. Probe terminals to check for this condition.

Engine idle speed can be adversely affected by the following

1. If ECM thinks the vehicle is always in Neutral, idle will not be controlled to the specified Drive RPM.
2. Leaking injectors will cause fuel imbalance and poor idle quality due to different air/fuel ratios in each cylinder. See appropriate CHART A7. Refer to the appropriate «5.0L/5.7L VINS [F,8] PFI "A" CHARTS»(/chevrolet/camaro/iii-1985-1992/remont/testing-diagnostics/#50l57l-vins-f8-pfi-a-charts) article in this section.
3. Vacuum or crankcase leaks can affect idle.
4. When the throttle shaft or TPS is binding or sticking in an open throttle position, the ECM does not know the vehicle has stopped and does not control idle.
5. Check air management system for intermittent air to ports while in "closed loop".
6. In addition to electrical control of EGR, be sure to examine the EGR valve for proper seating.
7. Faulty battery cables can result in voltage variations. The ECM will try to compensate by adjusting engine RPM. This results in erratic idle speeds.
8. The ECM will compensate for A/C compressor clutch loads. Loss of the A/C "on" signal would be most apparent in Neutral.
9. Contaminated fuel can adversely affect idle.
10. Perform injector balance test, see CHART C2A. If all checks okay, see TROUBLE SHOOTING in the CEC TESTS W/O CODES article in this section.

Flow Chart - Idle Air Control (F & "Y" Bodies). Scheme 268

Flow Chart - Idle Air Control (F & "Y" Bodies). Scheme 269

CHART C3 - CANISTER PURGE CHECK ("F" & "Y" BODIES)

Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when de-energized. The ECM supplies a ground on circuit No. 428 to energize the solenoid.

Note. Test numbers refer to test numbers on diagnostic chart.

1. This test checks to see if the solenoid is open or closed. The solenoid is normally energized in this step. It should be closed.
2. This test checks for open or grounded solenoid circuit.
3. Completes functional check by grounding ALDL "test" terminal. This should normally energize the solenoid and allow the vacuum to drop.

Flow Chart - Canister Purge Check ("F" & "Y" Bodies). Scheme 270

Flow Chart - Canister Purge Check ("F" & "Y" Bodies). Scheme 271

CHART C4 - IGN SYSTEM CHECK (5.0L/5.7L "F"/"Y" BODIES W/ HEI)

Note. Test numbers refer to test numbers on diagnostic chart.

1. 1) This test checks for proper output from the ignition system. The spark plug tester requires a minimum of 25,000 volts to fire. This tester should be used in case of an ignition misfire because the DIS system may provide enough voltage to run the engine but not enough to fire a spark plug under heavy load.
2. 1A) If spark occurs with EST connector disconnected, pick-up coil output is too low for EST operation.
3. 2) Normal reading during cranking is about 8-10 volts.
4. 3) This test checks for a shorted module or grounded circuit from the ignition coil to the module. The distributor module should be turned off so normal voltage should be about 12 volts. If the module is turned on, the voltage would be low, but should be above one volt. This could cause the ignition coil to fail from excessive heat. With an open ignition coil primary winding, a small amount of voltage will leak through the module from the battery to the tachometer terminal.
5. 4) Checks the voltage output with the pick-up coil triggering the module. A spark indicates that the ignition system has sufficient output, however, intermittent no-starts or poor performance could be the result of incorrect polarity between the ignition coil and the pick-up coil.
6. 5) This test checks for an open in the module or the circuit to it. Applying 12 volts to terminal "P" will turn the module on and the voltage should drop to about 7-9 volts.
7. 6) This should turn off the module and cause a spark. If no spark occurs, the fault is most likely in the ignition coil because most module problems would have been found before this point in the test procedure. Using a module tester could determine which is at fault.

Flow Chart - Ign. System (5.0L/5.7L "F"/"Y" Bodies W/ HEI). Scheme 272

Flow Chart - Ign. System (5.0L/5.7L "F"/"Y" Bodies W/ HEI, 1 Of 2). Scheme 273

Flow Chart - Ign. System (5.0L/5.7L "F"/"Y" Bodies W/ HEI, 2 Of 2). Scheme 274

CHART C5 - ELECTRONIC SPARK CONTROL ("F" & "Y" BODIES)

The Electronic Spark Control (ESC) system on these vehicles consists of a knock sensor and an ESC controller which sends a voltage signal to the ECM. As engine knock is detected by the knock sensor, a signal is sent to the ESC controller. The controller responds to this knock signal by cutting off current to ECM on circuit No. 485. The ECM will then retard timing if engine speed is greater than 850 RPM.

Note. Test numbers refer to test numbers on diagnostic chart.

1. If a Code 43 is not set, but a knock signal is indicated while running at 1500 RPM, listen for an internal engine noise. Under a no load condition, there should be no detonation. If knock is indicated, an internal engine problem may exist.
2. Usually, a knock signal can be generated by tapping on the right exhaust manifold. This test can also be performed at idle. Test No. 1 was run at 1500 RPM to determine if a constant knock signal was present, which would affect engine performance.
3. This tests whether the knock signal is due to the sensor, a basic engine problem, or the ESC module.
4. If the module ground circuit is faulty, the ESC module will not function correctly. The test light should light, indicating the ground circuits are okay.
5. Contacting circuit No. 496 with a test light to 12 volts should generate a knock signal to determine if the knock sensor is faulty, or if the ESC module can't recognize a knock signal.

Most "Scan" testers have 2 different parameter positions to diagnose the ESC system. The knock signal can be monitored to see if the knock sensor is detecting a knock condition and if the ESC module is functioning. The knock signal should display "YES", whenever detonation is present. The knock retard position on the "Scan" tester displays the amount of spark retard the ECM is commanding. The ECM can retard the timing up to 20 degrees. Also, see additional reasons for detonation/spark knock in TROUBLE SHOOTING in the CEC TESTS W/O CODES article in this section.

Flow Chart - Electronic Spark Control ("F" & "Y" Bodies). Scheme 275

Flow Chart - Electronic Spark Control ("F" & "Y" Bodies). Scheme 276

CHART C6B - AIR MANAGEMENT CHECK (5.0L/5.7L "F"/"Y" BODIES)

Air management is controlled by a pressure operated port valve and a converter valve, each with an ECM controlled solenoid. When the solenoid is grounded by the ECM, air pressure will activate the valve and allow pump air to be directed as follows

1. Cold Mode - Port solenoid is grounded by the ECM. Pump air then goes to exhaust ports.
2. Warm Mode - Port solenoid is de-energized. Converter solenoid is grounded by the ECM. Pump air then goes to converter.
3. Divert Mode - Neither solenoid is grounded by the ECM. Pump air is diverted to atmosphere.

Note. Test numbers refer to test numbers on diagnostic chart.

1. This test is a system functional check. Air is directed to exhaust ports during "open loop". All engine starts are in "open loop", even on a warm engine. Since the air-to-ports time may be very short on a warmed-up vehicle, prepare to observe port air prior to engine start up. This can be done by squeezing air hose.
2. This should normally set a Code 22. When any code is set, the ECM opens the ground to the converter solenoid and allows air to divert to atmosphere. This checks for ECM response to a fault. A ground in the control valve circuit to the ECM would prevent divert action.
3. This checks for a grounded circuit to the ECM. Test light off is normal and would indicate that the circuit is not grounded.
4. Checks for an open in the solenoid control circuits. Grounding the "test" terminal should ground both solenoid circuits. Normally, the test light should be on, which indicates the problem is not in the ECM or wiring but at the solenoid connections or valve itself.
5. Checks for a grounded solenoid circuit. Test light off would indicate the circuit is okay and fault is in the valve.

Flow Chart - Air Management Check. Scheme 277

Flow Chart - Air Management Check (1 Of 2). Scheme 278

Flow Chart - Air Management Check (2 Of 2). Scheme 279

CHART C7 - EGR CHECK (5.0L/5.7L "F" & "Y" BODIES)

The EGR valve is controlled by a normally open Pulse Width Modulated (PWM) solenoid. The ECM turns the solenoid off to allow vacuum to pass to the EGR and turns the solenoid on to prohibit EGR operation. When EGR is commanded, the solenoid is turned on and off many times a second (duty cycle).

The duty cycle is calculated by the ECM based on information from the coolant, MAT, TPS and MAF sensors. Also, engine RPM and the Park/Neutral switch inputs affect EGR. There should be no EGR when in Park or Neutral and TPS is below a calibrated value or TPS is indicating Wide Open Throttle (WOT). With the ignition on and engine stopped, the EGR solenoid is de-energized. The solenoid, however, should be energized if the diagnostic "test" terminal is grounded with the ignition on and engine not running.

Note. Test numbers refer to test numbers on diagnostic chart.

1. This will test the solenoid to determine if it is capable of closing off the manifold vacuum from the EGR valve. The vacuum may bleed off slowly but this should not be considered a fault.
2. As soon as backpressure is available at the EGR valve, the bleed portion in the valve should open and cause the valve to go to its seated position.
3. The EGR valve will be inoperative if the Park/Neutral switch is misadjusted or defective. Use "Scan" tester and check Park/Neutral switch. See appropriate CHART C1A.

Flow Chart - EGR Check (5.0L & 5.7L "F" & "Y" Bodies). Scheme 280

Flow Chart - EGR Check (5.0L & 5.7L "F" & "Y" Bodies). Scheme 281

CHART C8A - TORQUE CONVERTER CLUTCH (TCC) 5.0L/5.7L "F" BODY, 1 OF 2)

The purpose of the Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter stage when the vehicle is in a cruise condition. This allows the convenience of the automatic transmission and the fuel economy of a manual transmission. The heart of the system is a solenoid located inside the automatic transmission which is controlled by the ECM.

When the solenoid coil is activated, the TCC is applied through a mechanical coupling from the engine to transmission. When the transmission solenoid is de-energize, the TCC is released which allows the torque converter to operate in the conventional manner (fluidic coupling between engine and transmission). The ECM turns on the TCC when coolant temperature is greater than 149°F (65°C), TPS is not changing and vehicle speed is greater than a specified value.

Note. Test numbers refer to test numbers on diagnostic chart.

1. When a test light is connected from ALDL terminal "F" to ground, a test light on indicates battery voltage is okay and the TCC solenoid is disengaged.
2. When the diagnostic "test" terminal is grounded, the ECM should energize the TCC solenoid and the test light should go out.

A "Scan" tester only indicates when the ECM has turned on the TCC driver (grounded circuit No. 422). This does not confirm that the TCC has engaged. To determine if TCC is functioning properly, observe engine RPM. RPM should decrease when the "Scan" tester indicates the TCC driver has turned on. The switches will not prevent TCC from functioning, but will affect TCC lock and unlock points. If the 4th gear switch circuit is always open the TCC may engage as soon as sufficient oil pressure is reached.

Torque Converter Clutch (5.0L/5.7L "F" Body). Scheme 282

Check Made In This Chart Will Not Prevent The TCC From Working, But Will Affect Engagement Or Disengagement Points

Torque Converter Clutch (5.0L/5.7L "F" Body). Scheme 283

CHART C8A - TORQUE CONVERTER CLUTCH (TCC) 5.0L/5.7L "F" BODY, 2 OF 2)

A 4th gear switch (mounted in the transmission) opens when the transmission shifts into 4th gear. This switch is used by the ECM to modify TCC lock and unlock points (when in a 4-3 downshift).

Note. Test numbers refer to test numbers on diagnostic chart.

1. Unless the switch or circuit No. 446 is open, the "Scan" tester should display "NO", indicating the transmission is not in 4th gear. The 4th gear switch should only be open while in 4th gear.
2. This test determines if the ECM and wiring are okay. Grounding circuit No. 446 should cause the "Scan" tester to display "NO", indicating the transmission is not in 4th gear.
3. Checks the operation of the 4th gear switch. When the transmission shifts into 4th gear, the switch should open and the "Scan" tester should display "YES".
4. Disconnecting the TCC connector simulates an open switch to determine if circuit No. 446 is shorted to ground or the problem is in the transmission.

A road test may be necessary to verify the problem. If the "Scan" tester indicates TCC is turning on and off erratically, check the status of the 4th gear switch to be sure it is not changing under a steady throttle position. If the switch is changing, check connections and wire routing carefully. If the 4th gear switch is always open the TCC may engage as soon as sufficient oil pressure is reached.

Torque Converter Clutch (5.0L/5.7L "F" Body). Scheme 284

Using A "Scan" Tool, Check The Following And Correct If Necessary

1. Coolant Temperature Should Be Above 65°C
2. TPS - Be Sure TPS Signal Is Not Erratic
3. VSS - Be Sure "Scan" Displays VSS With Drive Wheels Turning
4. Codes - If Code 24 Is Present, See Code Chart 24

Torque Converter Clutch (5.0L/5.7L "F" Body). Scheme 285

SHIFT INDICATOR LIGHT (MANUAL TRANSMISSION

The shift light indicates the best transmission shift point for maximum fuel economy. The light is controlled by the ECM and is turned on by grounding circuit No. 422/456. To control the shift light, the ECM uses information from the CTS, TPS, VSS and ignition module reference (RPM). The ECM uses the measured RPM and the vehicle speed to calculate what gear the vehicle is in. This calculation determines when the shift light should be turned on.

Note. Test numbers refer to test numbers on diagnostic chart.

1. This test should not turn on the shift light. If the light is on, there is a short to ground in circuit No. 422/456 wiring or a fault in the ECM.
2. When the diagnostic "test" terminal is grounded, the ECM should ground circuit No. 422/456 and the shift light should come on.
3. This checks the shift light circuit up to the ECM connector. If the shift light illuminates, the ECM connector is faulty or the ECM does not have the ability to ground the circuit.

Flow Chart - Shift Light Indicator (5.0L "F" Bodies). Scheme 286

Flow Chart - Shift Light Indicator (5.0L "F" Bodies). Scheme 287

COOLING FAN CIRCUIT (5.0L/5.7L "F" BODY, 1 OF 2)

The cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and fan control switch. The fan should run, if coolant temperature is greater than 226°F (108°C). Battery voltage is supplied to the fan relay on terminal "E" and ignition voltage to terminal "D".

Grounding circuit No. 335 (relay terminal "F") will energize the relay and supply battery voltage to the fan motor. Once the fan relay is energized by the ECM, it will remain on for a minimum of 30 seconds. The ECM will remove the ground to circuit No. 335 if vehicle speed is greater than 40 MPH or the engine is overheating.

The fan control switch is mounted in the A/C high pressure line and will open when head pressure exceeds 233 psi (16 kg/cm 2 )) and this input causes the ECM to ground circuit No. 335. If Code 14 or 15 sets or the ECM is operating in the fuel back-up mode, the ECM will turn on the cooling fan.

If there is an overheating problem, it must be determined if the complaint was due to an actual boilover or if the hot light or temperature gauge indicates overheating.

If the gauge or light indicates overheating but no boilover is detected, the gauge circuit should be checked. The gauge accuracy can also be checked by comparing the coolant sensor reading using a "Scan" tester and comparing its reading with the gauge reading.

If the engine is actually overheating and the gauge indicates overheating, but the cooling fan is not coming on, the coolant sensor has probably shifted out of calibration and should be replaced. If the engine is overheating and the cooling fan is on, the cooling system should be checked.

Flow Chart, (1 of 2) - Cooling Fan Circuit ("F" Body). Scheme 288

Flow Chart, (1 of 2) - Cooling Fan Circuit ("F" Body, 1 Of 2). Scheme 289

Flow Chart, (1 of 2) - Cooling Fan Circuit ("F" Body, 2 Of 2). Scheme 290

COOLING FAN CIRCUIT (5.0L/5.7L "F" BODY, 2 OF 2)

The cooling fan is totally controlled by the ECM based on inputs from the coolant sensor and fan control switch. The fan should run if coolant temperature is greater than 226°F (108°C). Battery voltage is supplied to the fan relay on terminal "E" and ignition voltage to terminal "D".

Grounding circuit No. 335 (relay terminal "F") will energize the relay and supply battery voltage to the fan motor. Once the fan relay is energized by the ECM, it will remain on for a minimum of 15 seconds. The ECM will remove the ground to circuit No. 335 if vehicle speed is greater than 40 MPH, unless the engine is overheating.

The fan control switch is mounted in the A/C high pressure line and will open when head pressure exceeds 233 psi (16 kg/cm 2 ). This input causes the ECM to ground circuit No. 335. If Codes 14 or 15 set, or the ECM is operating in the fuel back-up mode, the ECM will turn on the cooling fan.

If there is a problem of overheating, it must be determined if the problem was due to actual boilover or if the hot light or temperature gauge indicated overheating.

If the gauge or light indicates overheating but no boilover is detected, the gauge circuit should be checked. the gauge accuracy can also be checked by comparing the coolant sensor reading using the "Scan" tester and comparing its reading with the gauge reading.

If the engine is actually overheating and the gauge indicates overheating, but the cooling fan is not coming on, the coolant sensor has probably shifted out of calibration and should be replaced. If the engine is overheating and the cooling fan is on, the cooling system should be checked.

Flow Chart, (2 of 2) - Cooling Fan Circuit ("F" Body). Scheme 291

Flow Chart, (2 of 2) - Cooling Fan Circuit ("F" Body). Scheme 292

Component Locations, 5.0L (VIN F) & 5.7L (VIN 8). Scheme 293

ECM Terminal Identification, 5.0L (VIN F) & 5.7L (VIN 8). Scheme 294

Wiring Diagram, 5.0L (VIN F) & 5.7L (VIN 8). Scheme 295

See also:
• 5.0L/5.7L VINS [F,8] PFI "A" CHARTS