3.7l &5.2l Efc System Dodge Ram Van II

DESCRIPTION

Note. Some 3.7L and 5.2L models use the Spark Control Computer with Spark Advance and Throttle Control systems. Only 3.7L models with Holley 6145 and 5.2L models with Holley 6280 feedback carburetors use oxygen sensor feedback system.

The Electronic Fuel Control (EFC) system is an electronically controlled system that closely controls ignition timing and, on 3.7L and 5.2L models with feedback system, the air/fuel ratio. The Spark Control Computer (SCC) is the heart of the system.

The SCC provides the capability of igniting a lean air/fuel mixture under various engine operating conditions. Also, during closed loop operation on models with feedback system, the computer maintains an air/fuel ratio close to the ideal 14.7:1.

OPERATION

The EFC system consists of the following sub-systems: fuel control (models with feedback system), electronic throttle control, spark control, data sensors, Spark Control Computer (SCC), electronic exhaust gas recirculation (EGR), electronic air switching and catalytic converter.

CODE-TO-TEST MENU

TROUBLE CODE TEST INDICATION CHART

FUEL CONTROL

Some 3.7L models are equipped with a Holley 6145 1-barrel feedback carburetor. Some 5.2L models are equipped with a Holley 6280 2-barrel feedback carburetor. These carburetors contain an electronically operated duty cycle solenoid. This solenoid meters air flow of the carburetor fuel circuit and operates in parallel with the conventional fixed main metering jets. The computer controls the operation of the solenoid with electrical signals, in response to input from data sensors. (Scheme 53)

View of Holley 6145 Feedback Carb. W/ Duty Cycle Solenoid Used on some 3.7L models. Scheme 53

When the solenoid is de-energized by the computer, the solenoid valve spring pushes upward through the main system fuel valve. When de-energized, the solenoid main metering orifice is fully uncovered, providing the richest mixture for any given air flow.

When the solenoid is energized by the computer, the solenoid main metering orifice is fully sealed. This solenoid position offers the leanest mixture within the carburetor for any given air flow.

Main system fuel may be regulated between richest and leanest mixture conditions by controlling the amount of time that the solenoid is energized and de-energized. The computer controls the length of time that the solenoid is energized relative to total solenoid operation time.

This time interval is determined by engine operating conditions and/or oxygen sensor signals. In this manner, the ideal air/fuel ratio can be constantly maintained.

ELECTRONIC THROTTLE CONTROL

The Electronic Throttle Control system and 2 electric timers are incorporated within the SCC. A solenoid, mounted on the carburetor, is energized whenever the air conditioning, heater, rear window defogger or electric timers are activated. The 2 timers operate when the throttle is closed, providing a 2 second time delay, or after engine is started.

SPARK CONTROL

Spark Control allows the computer to determine the exact instant that ignition is required. It then signals ignition coil to Produce electrical impulses which fire the spark plugs. The computer eliminates the need for either vacuum advance units or centrifugal advance weights. Spark control operates in one of the following modes

Start Mode

During cranking, an electrical signal from the distributor is fed into the computer. The computer determines spark timing based on this signal. Spark timing while in "start" mode does not vary as it is dependent upon distributor position.

Run Mode

With the engine started and operating normally, spark timing is controlled by the computer, based upon information received from the data sensors.

Spark timing and dwell cannot be adjusted in the run mode. If the computer fails, the system will go into "start" mode. This enables vehicle to be driven in for repair, but performance and fuel economy will be poor. If start mode fails, engine will not start or run.

The amount of spark advance in "run" mode is determined by engine speed, temperature and engine vacuum. When spark advance occurs is dependent upon the following conditions

Advance From Vacuum

Advance based upon engine vacuum is allowed by the computer when the carburetor switch is open. The amount of advance is programmed into the computer and is proportional to vacuum, temperature and engine speed (RPM).

Advance From Speed

Advance based upon engine speed (RPM) is controlled by the computer when the carburetor switch is open. If carburetor switch closes, advance from speed will be canceled.

DATA SENSORS

Each sensor furnishes electrical impulses to the SCC. The SCC computes ignition timing and air/fuel mixture ratio necessary to maintain proper engine operation. The function of each sensor is closely related to each of the other sensors. Operation of each sensor is as follows

Magnetic Pick-up Assembly

The magnetic pick-up assembly consists of 2 pick-up coils, the start pick-up coil and run pick-up coil. Both pick-up coils are located in the distributor and operate as follows

1. Start Pick-Up Coil - Supplies a signal to SCC which will cause the spark plugs to fire at a fixed amount of advance during cranking only. This coil is permanently attached to distributor and the amount of advance is determined by distributor position. (Scheme 54)
2. Run Pick-Up Coil - Once engine begins to run, the start pick-up coil signal is by-passed and the run pick-up coil supplies advance information to the SCC. The SCC then modifies advance in response to engine operating conditions as reported by other sensors.

View of Distributor with Cap & Rotor Removed 3.7L distributor is shown, 5.2L distributor similar. Scheme 54

Coolant Temperature Sensor/Switch

The coolant sensor and switch inform the SCC when engine has reached normal operating temperature. Coolant temperature information is used to control ignition timing while engine is cold.

Vacuum Transducer

This sensor is mounted on the computer and provides the computer with a signal indicating the amount of engine vacuum. Engine vacuum is used by the computer to determine how much to advance or retard the ignition timing and when to adjust air/fuel mixture.

Carburetor Switch

Located on the end of idle stop, the carburetor switch informs the computer when the engine is at idle. When carburetor switch contacts throttle lever ground, the computer will cancel spark advance and prevent air/fuel ratio adjustment.

Oxygen (O2) Sensor

The oxygen sensor is only used on vehicles with feedback carburetors. The sensor is located in the exhaust manifold. Sensor informs the computer of the amount of oxygen present in exhaust gases. The amount of oxygen is proportional to mixture strength. The computer adjusts the air/fuel ratio to maintain ideal operating conditions and optimum efficiency of the 3-way catalyst system.

Charge Temperature Switch

This sensor is located in the intake manifold. The switch is closed when intake charge (air/fuel mixture) is below 60°F (16°C). This prevents EGR timer function and EGR valve operation. When temperature is above 60°F (16°C), the switch opens, allowing EGR timer to time out and EGR valve to operate.

Coolant Temperature/Charge Temperature Sensor

This sensor is located on the intake manifold to monitor engine temperature. It is located either in a coolant passage or an intake manifold runner, depending upon application. The sensor signals the SCC when to operate the air switching, EGR and spark advance systems.

SPARK CONTROL COMPUTER

The Spark Control Computer (SCC) is mounted on the left inner fender panel (Pickup models) and center of the firewall (Van models). The SCC consists of a printed circuit board which simultaneously receives signals from all data sensors and analyzes these signals to determine spark advance and, on models with feedback carburetor, the air/fuel mixture. Incorporated within the computer are the electronics for throttle control, EGR and air switching systems. After determining spark advance, the computer operates the engine feedback system (on models so equipped) in one of the following modes

Open Loop

During cold engine operation, the air/fuel ratio is controlled by information programmed into the computer by the manufacturer. Until normal operating temperature is reached, the air/fuel mixture will be fixed at a rich level to allow proper engine warm-up. During this mode of operation, air from the air pump is injected "upstream" in the exhaust manifold to assist in heating up the oxygen sensor.

Closed Loop

Once normal engine operating temperature is achieved, the air/fuel ratio is controlled by the computer based upon information received from the oxygen sensor.

Electronic Exhaust Gas Recirculation (EGR)

The electronic EGR system is incorporated within the SCC and is used on all models equipped with Electronic Spark Advance (ESA). This system prevents EGR flow until engine has reached normal operating temperature (after a predetermined length of time).

Electronic Air Switching

The electronic air switching system is incorporated within the SCC and is used only on California and High Altitude models. This system directs the flow of air from the air pump either "upstream" or "downstream" after engine has reached operating temperature and a specified period of time has elapsed.

CATALYTIC CONVERTER

All models are equipped with one or two catalytic converters to reduce emissions of all 3 major pollutants: HC, CO and NOx. In addition to the main converter, some models are equipped with a "mini-ox" converter. The mini-ox is located immediately below the exhaust manifold-to-exhaust pipe connection (left side on V8) and is significantly smaller than the main converter, which is located farther downstream.

Note. External similarities exist between converter systems. However, extreme care must be exercised during replacement of converters due to internal design differences.

BASIC TEST PREPARATION

Note. DO NOT proceed with testing unless the basic checks have been performed.

A malfunction in the EFC system may result in engine surge, hesitation, rough idle and/or poor fuel economy. Before performing any tests, check all vacuum and electrical wiring for proper routing and connections and check for exhaust and intake manifold leaks. DO NOT proceed with testing unless the basic checks have been performed.

The Spark Control Computer controls ignition timing and air/fuel mixture (on models so equipped). When testing requires that either harness connector be disconnected from computer, DO NOT remove grease from either connector or terminals in computer.

The grease is used in order to prevent moisture from corroding the terminals. If there is not at least 1/2" of grease on bottom of computer connector terminals, apply a liberal amount of multipurpose grease (Mopar No. 2932524) over entire end of plug before reinstalling.

ENTERING ON-BOARD DIAGNOSIS

1. Attach the Chrysler Diagnostic Read-Out Box (C-4805) to self-test connector. The connector is located in the engine compartment at the left shock tower (pickup models) and center of firewall (van models).
2. Place the read/hold switch in the "READ" position. Open the carburetor switch by placing the fast idle screw on the highest step of the fast idle cam. Turn the ignition switch to the "RUN" position and wait for "00" to display on the read-out box.
3. Move the read/hold switch to the "HOLD" position. Record all codes that appear. The display codes may be stopped by switching the to the "READ" position. Codes will continue when the read-out box is switched back to the "HOLD" position.

FAULT CODE IDENTIFICATION

When a fault code is displayed on the diagnostic read-out box, it indicates the SCC has recognized an abnormal signal in the system. Fault codes indicate the result of a failure, but do not always identify the failed component.

Code 00

This code indicates the diagnostic read-out box is receiving power.

Code 88

This code implies the "start of diagnostic mode." If this code is not displayed first, trouble codes will be inaccurate.

Code 55

This is the "end of diagnostic mode." This code will always appear as the final code after all other trouble codes have been displayed.

Code 11

Problem with O2 solenoid control circuit.

Code 12

Problem in the transmission unlock relay.

Note. Ignore this code on manual transmission models.

Code 13

Indicates a problem in the air switching control solenoid system.

Code 14

Indicates the battery has been disconnected within the last 20-40 times the ignition switch has been turned to the "ON" position.

Code 17

Indicates a problem in the electronic throttle control solenoid system.

Code 18

Indicates a problem in the EGR solenoid.

Code 21

Problem with the distributor pick-up system.

Code 22

O2 system is stuck in the full lean position.

Code 23

O2 system is stuck in the full rich position.

Code 24

Indicates a problem in the computer.

Code 25

Problem in the radiator fan coolant sensor portion of the engine temperature dual sensor system.

Code 26

Problem in the engine temperature portion of the engine temperature dual sensor system.

Code 28

Problem in the distance sensor system.

Code 31

Indicates the engine has not been cranked since the battery was disconnected.

Code 32

Indicates a problem with the computer.

Code 33

Indicates a problem with the computer.

ACTUATOR TEST CODES

Place the system into Diagnostic Test Mode and wait for Code 55 to appear on the display. Press the ATM button to activate the display. If a specific ATM test is desired, depress ATM button until the desired code is displayed. The computer will turn the selected circuit on and off for up to 5 minutes, until the ATM button is pressed again or the ignition is turned off.

Code 91

Oxygen feedback solenoid activated.

Code 92

Transmission unlock relay activated (A/T).

Code 93

Air switching solenoid activated.

Code 97

Electronic throttle control solenoid activated.

Code 98

EGR solenoid activated.

SENSOR READ TEST CODES

1. The sensor read test checks each circuit for proper operation. If correct code does not appear on the display during the test, the circuit and components must be checked. Place the system in Diagnostic Test Mode and wait for Code 55 to appear on the display.
2. Press the ATM button to activate the display. If a specific sensor read test is desired, hold the ATM button down until the desired code is displayed. Slide the read/hold switch to the "HOLD" position to display the corresponding sensor output level.

Note. Since the sensor access codes are the same as some ATM test codes, the ATM test circuit will turn on before moving the read/hold button to the "HOLD" position.

With 0-5 in. Hg vacuum applied to the transducer, display should be "01" when the read/hold switch is moved to the "HOLD" position. With 5-15 in. Hg vacuum applied to the transducer, display should be "02" when the read/hold switch is moved to the "HOLD" position. With more than 15 in. Hg vacuum applied to the transducer, display should be "03" when the read/hold switch is moved to the "HOLD" position.

This tests the engine coolant sensor circuit. With an engine temperature of less than 50°F (10°C), display should be "01" when the read hold switch is moved to the "HOLD" position. With an engine temperature of 50-100°F (10-38°C), display should be "02" when the read hold switch is moved to the "HOLD" position. With an engine temperature of greater than 100°F (38°C), display should be "03" when the read hold switch is moved to the "HOLD" position.

This tests the charge temperature switch circuit. With the engine cold, display should be "01". With the engine at normal operating temperature, display should be "03".

Code 96

This tests the vehicle distance sensor circuit. If the switch is closed, display should be "01". If the switch is open, display should be "02".

SWITCH TEST CODES

1. Place the system in Diagnostic Test Mode and wait for Code 55 to appear on the display. Ensure that both air conditioning and defroster switches are off. Press the ATM button and immediately move the read/hold switch to the "READ" position. Wait for Code 00 to appear on the display.
2. Turn the air conditioning switch to the "ON" position. If the computer is receiving input, the display will change to "88" when the switch is turned on and to "00" when the switch is turned the "OFF" position. Repeat the test for the defroster switch. Code 00 - Air conditioning and defroster are off. Code 88 - Air conditioning or defroster are on.

NS1 - CHECKING FOR SPARK AT PLUG WIRES

1. Disconnect any spark plug wire and insert an insulated screwdriver into spark plug wire. (Scheme 55) Hold screwdriver shaft about 1/4" from a good ground. Have an assistant crank engine.
2. There should be a good spark between screwdriver and ground. If there is spark, proceed to «NS2 - CHECKING FOR FUEL IN CARBURETOR»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__ns2-checking-for-fuel-in). If no spark, proceed to «NS5 - IGNITION COIL SPARK CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).

Checking for Spark At Plug Wires. Scheme 55

NS2 - CHECKING FOR FUEL IN CARBURETOR

1. Remove air cleaner cover. Open throttle several times by hand. Look for fuel spray from accelerator pump nozzle in carburetor throat. (Scheme 56) There should be fuel spraying from the accelerator pump nozzle while opening throttle.
2. If fuel spray tests okay, proceed to «NS3 - FUEL FOULED SPARK PLUGS CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__ns3-fuel-fouled-spark-plugs). If no fuel spray, proceed to «NS7 - FUEL PUMP PRESSURE CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).

Checking for Fuel in Carburetor. Scheme 56

NS3 - FUEL FOULED SPARK PLUGS CHECK

Remove spark plugs. Inspect spark plug tips for wet fuel. Spark plugs should be dry. If spark plugs are dry, proceed to NS4 - ENGINE TIMING CHECK . If spark plugs are wet with fuel, clean and reinstall.

NS4 - ENGINE TIMING CHECK

1. Connect timing light to engine. Have an assistant crank engine while you look at the timing marks. (Scheme 57) Timing should be 0-16° BTDC. If timing is okay, check valve timing and compression.
2. If timing is not okay, set timing to 10° BTDC while cranking. Engine should start. If engine starts, set timing to specification. If engine does not start, check valve timing and compression.

Engine Timing Check. Scheme 57

Scheme 58

1. Disconnect secondary coil wire from distributor cap. Hold coil wire 1/4" from a good ground. (Scheme 58) Crank the engine. There should be spark between the coil wire and ground. (Scheme 58): Ignition Coil Wire
2. If there is spark, check for problem in distributor cap, rotor or secondary wires. Repair or replace as necessary. If no spark, check coil wire resistance. (Scheme 59) Resistance should be 250-600 ohms per INCH or 3000-7200 ohms per foot. If resistance is within specifications, proceed to «NS6A - CHECKING PRIMARY IGNITION SYSTEM FOR FAULT CODES»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system). If resistance exceeds specifications, replace coil wire.

Ignition Coil Spark Check. Scheme 59

Scheme 60

1. Connect Diagnostic Read-Out Box (C-4805) to connector near left front shock tower. Set the read/hold switch to the "READ" position. Open the carburetor switch by placing the fast idle speed adjusting screw on the highest step of the fast idle cam. (Scheme 60): Diagnostic Read-Out Box
2. Turn the ignition switch to the "RUN" position and wait for "00" to appear on read-out box display. Move read/hold switch to the "HOLD" position. Record all codes. If Codes 88-55 or 88-14-55 appear, there are NO fault codes. Proceed to «NS6B - IGNITION COIL PRIMARY WINDINGS RESISTANCE CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).
3. If Codes 88-21-55 or 88-14-21-55 appear, fault is in distributor pick-up coil circuit. Proceed to «NS6C - DISTRIBUTOR DUAL PICK-UP COIL RESISTANCE CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__ns6c-distributor-dual-pick-up-coil) for vehicles with dual pick-up distributor. Proceed to «NS6D - DISTRIBUTOR SINGLE PICK-UP COIL RESISTANCE CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) for vehicles with single pick-up distributor.
4. If Codes 88-21-26-28-55 or 88-14-21-26-28-55 appear, fault is in distributor/sensor ground circuit. Repair wire to terminal "9" of computer 10-pin connector for an open circuit.
5. If NO Code 88, proceed to «NS6F - VOLTAGE SUPPLY TO COMPUTER CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).

Scheme 61

Scheme 62

Scheme 63

1. Ensure ignition is off. Connect an ohmmeter between the ignition coil positive and negative terminals. (Scheme 61) Ohmmeter reading should be 1-2 ohms. If resistance is not within specifications, replace ignition coil. (Scheme 61): Checking Coil Positive & Negative Terminals
2. If resistance is within specifications, disconnect coil secondary wire from coil. Connect ohmmeter to the coil negative terminal and the secondary terminal. (Scheme 62) Ohmmeter reading should be 8500-17,500 ohms. (Scheme 62): Checking Coil Negative & Secondary Terminal
3. If resistance is not within specifications, replace ignition coil. If resistance is okay, check coil with a load test. If coil is okay, disconnect 10-pin connector from computer. Connect voltmeter between terminal "1" and ground. (Scheme 63) (Scheme 63): Checking 10-Pin Terminal No. 1 & Ground
4. Turn ignition switch to "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. If voltage is not within specifications, repair primary circuit to ignition coil for open or short circuit.
5. If voltage is okay, check terminal in terminal "1" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer.

NS6C - DISTRIBUTOR DUAL PICK-UP COIL RESISTANCE CHECK

1. Disconnect the computer 10-pin connector. Connect an ohmmeter between 10-pin connector terminals "5" and "9". (Scheme 64) Ohmmeter reading should show continuity.
2. If there is continuity, replace computer. If NO continuity, repair dual pick-up coil ground circuit for an open circuit to the wiring harness splice.

Checking 10-Pin Terminal Nos. 5 & 9. Scheme 64

Scheme 65

1. Disconnect distributor pick-up coil connector. Connect an ohmmeter between pick-up coil connector terminals. (Scheme 65) Ohmmeter reading should be 150-900 ohms. (Scheme 65): Checking Distributor Connector
2. If there is zero resistance, an open circuit or resistance is not within specifications, replace pick-up coil. If resistance is okay, reconnect distributor start pick-up coil connector. Disconnect the computer 10-pin connector. Connect ohmmeter between 10-pin connector terminals "5" and "9". (Scheme 64) Ohmmeter reading should be 150-900 ohms.
3. If there is zero resistance or an open circuit, repair wiring to distributor pick-up coil for open or short circuits. If resistance is okay, check distributor pick-up coil air gap. If okay, check terminal in terminal "5" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer.

Scheme 66

1. Reconnect the distributor pick-up coil connector. Disconnect the computer 10-pin connector. Connect an ohmmeter to the 10-pin connector terminals "5" and "9". Ohmmeter reading should be 150-900 ohms. (Scheme 66): Checking 10-Pin Terminal Nos. 5 & 9
2. If there is zero resistance or an open circuit, repair wiring to distributor pick-up coil for open or short circuits. If resistance is okay, check distributor pick-up coil air gap. If okay, check terminal in terminal "5" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer.

Scheme 67

Scheme 68

1. Turn ignition off. Disconnect 10-pin connector from the computer. Connect voltmeter to connector terminal "2" and ground. (Scheme 67) Turn ignition switch to "RUN" position. Voltmeter reading should be within one volt of battery voltage. (Scheme 67): Checking 10-Pin Terminal No. 2 To Ground
2. If voltage is not within specifications, repair wiring to terminal "2" for an open circuit to ignition switch. Turn ignition off. Connect ohmmeter to connector terminal "10" and ground. (Scheme 68) Ohmmeter reading should show continuity with NO resistance. (Scheme 68): Checking 10-Pin Terminal No. 10 To Ground
3. If circuit does not have continuity, repair open circuit. If circuit has continuity, with resistance, repair as required. If circuit has continuity with no resistance, check terminals in terminals "2" and "10" to ensure they are not spread apart causing a poor connection. If connections are okay, replace computer.

Scheme 69

Scheme 70

Scheme 71

1. Connect fuel pump pressure gauge to fuel line at carburetor. (Scheme 69) Plug fuel return line at fuel filter. Crank engine for at least 10 seconds. Fuel pump pressure should be at least 2-5 psi. (Scheme 69): Fuel Pump Pressure Check
2. If fuel pump pressure is okay, repair carburetor fuel inlet circuit. If fuel pressure is not within specifications, reconnect fuel line at carburetor. Connect fuel pump pressure gauge to fuel line before fuel filter. (Scheme 70) Crank engine for at least 5 seconds. (Scheme 70): Reconnect Fuel Line At Carburetor
3. Fuel pump pressure should be at least 2-6 psi. If fuel pressure is okay, replace fuel filter. If fuel pressure is not within specifications, disconnect pressure gauge. Disconnect fuel pump inlet line and connect a vacuum gauge to pump inlet. (Scheme 71) Crank engine for at least 10 seconds. (Scheme 71): Connect A Vacuum Gauge To Pump Inlet
4. Vacuum gauge should read at least 10 in. Hg vacuum. If vacuum is not within specifications, replace fuel pump. If vacuum is okay, check for restricted or plugged fuel lines, fuel tank vent or in-tank filter.

Scheme 72

1. Connect Diagnostic Read-Out Box (C-4805) to connector near left front shock tower. Place system into the diagnostic mode by setting the read/hold switch to the "READ" position. Open the carburetor switch by placing the fast idle speed adjusting screw on the highest step of the fast idle cam. (Scheme 72): Diagnostic Read-Out Box
2. Turn the ignition switch to the "RUN" position and wait for "00" to appear on read-out box display. Move read/hold switch to the "HOLD" position. Record all codes. If Codes 12-22-28-25-26 appear, proceed to «DRIVEABILITY TROUBLE CODE TEST INDICATION CHART»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).
3. Turn ignition switch to the "OFF" position. Disconnect the computer 14-pin connector for 1 minute and then reconnect it. Disconnect read-out box. Start engine and idle for 2 minutes. Turn engine off. Reconnect diagnostic read-out box. Place system into diagnostic mode and record all codes.
4. If the same code appears before and after engine is started, the problem still exists. Proceed to «DRIVEABILITY TROUBLE CODE TEST INDICATION CHART»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system). If a code does not reappear after engine is started, the problem no longer exists, but was intermittent. Using wiring diagram as a guide, check for loose or corroded wiring connections in the circuit. Go to «DR1D - INTERMITTENT FAILURE»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__dr1d-intermittent-failures).

DRIVEABILITY TROUBLE CODE TEST INDICATION CHART

DR1B - CHECKING COMPUTER CONTROLLED COMPONENTS

Connect diagnostic read-out box to the engine harness connector. Place system into ATM Test Mode. Press and hold the ATM button until the first test code appears. Test components as follows

Diagnostic Read-Out Box. Scheme 73

Note. Used with oxygen feedback system only.

O2 sensor should start clicking. If O2 sensor does not click, replace it. With O2 sensor clicking, press and hold ATM button until the next test code appears.

Test Code 92

Note. Used on 3.7L man. trans. models only.

Shift indicator light on dash should start flashing. If the shift indicator light does not flash, repair circuit as needed. With shift indicator light flashing, press and hold ATM button until the next test code appears.

Transmission unlock relay should start clicking. If transmission unlock relay does not click, replace relay. If transmission unlock relay clicks, proceed to TEST 1C.

Test Code 93

Air switching solenoid should start clicking. If air switching solenoid does not click, replace solenoid. With air switching solenoid clicking, press and hold ATM button until the next test code appears.

Test Code 97

Open throttle and lightly press on the solenoid plunger. Solenoid plunger should move in and out. If solenoid plunger does not move, replace solenoid. With solenoid plunger moving in and out, press and hold ATM button until the next test code appears.

Test Code 98

EGR or canister purge control solenoid should start clicking. If EGR or canister purge control solenoid does not click, replace solenoid. If EGR or canister purge control solenoid clicks, turn ignition off. If problem occurs when cold, proceed to DR12 - FAST IDLE CAM LINKAGE & CHOKE CHECK . If problem occurs when warm, proceed to DR19 - CARBURETOR SWITCH CHECK .

Scheme 74

Scheme 75

Scheme 76

1. Connect diagnostic read-out box to the engine harness connector. Disconnect harness connector from the transmission unlock solenoid. Connect a voltmeter to the transmission unlock solenoid harness connector and ground. (Scheme 74) Put the system in ATM Test Mode, beginning with Test Code 92. (Scheme 74): Transmission Unlock Relay Identification
2. Voltmeter reading should pulsate between 2-10 volts. If voltmeter pulsates between 2-10 volts, turn ignition off. Connect a jumper wire to the transmission unlock solenoid and touch the other end of the wire to the battery positive terminal. (Scheme 75) (Scheme 75): Jumper Wire To Battery
3. The solenoid should click when the jumper wire touches the positive battery terminal. If the solenoid does not click, replace the solenoid. If the solenoid clicks, perform DR1B, beginning with Test Code 93.
4. If voltmeter does not pulsate between 2-10 volts, connect a jumper wire between transmission unlock relay terminals "1" and "2". (Scheme 76) The voltmeter should pulsate between 2-10 volts. If voltmeter pulsates, repair wire from terminal "1" to the harness splice for an open circuit. (Scheme 76): Transmission Unlock Relay Terminal Nos. 1 & 2
5. If voltmeter does not pulsate, connect a jumper wire to transmission unlock relay terminal "3" and the other end to positive battery terminal. (Scheme 77) Voltmeter should read within 1 volt of battery voltage. If voltage is okay, replace the solenoid. If zero volts, repair the wire from relay terminal "3" to the solenoid for an open circuit.

Transmission Unlock Relay To Battery. Scheme 77

DR1D - INTERMITTENT FAILURES

1. The majority of intermittent failures are caused by wiring and connections. The only way to find them is to try to duplicate the problem. Since the computer can remember where they are, the ATM Test Mode can be used in an attempt to locate them.
2. If the fault code does not reappear in DR1A, use the following procedure to try to locate an intermittent problem. If the following fault codes do not reappear, match the ATM Test Mode to the code first indicated by the following charts. ATM TEST MODE - EXCEPT FED. 3.7L WITH A/T & FED. 5.2L Fault Code ATM Test Mode 11 91 12 92 13 93 17 97 18 98 ATM TEST MODE - FED. 3.7L WITH A/T & FED. 5.2L Fault Code ATM Test Mode 11 91 12 92 13 93 17 97 18 98 SENSOR TEST MODE - FED. 3.7L WITH A/T & FED. 5.2L Fault Code Sensor Test Mode 24 91 25 93 26 92 28 96
3. Once in the correct test mode, wiggle all the connectors and wires in the circuit. When the bad connection or wire is located, the ATM test will stop. For Sensor Test Mode, the display on the read-out box will change.

Scheme 78

Scheme 79

Scheme 80

1. Connect diagnostic read-out box to the engine harness connector. Connect voltmeter to the O2 solenoid (Green wire) at the carburetor connector (2-pin connector on 6-cylinder and 4-pin connector on V8 models). (Scheme 78) Place system in ATM Test Mode 91. (Scheme 78): Checking Oxygen Sensor Circuit
2. Voltmeter reading should be pulsating and the solenoid should be clicking. If voltmeter reading is pulsating between 0-1 volt, replace the O2 solenoid. If voltmeter is not pulsating, but reads within 1 volt of battery voltage, turn ignition off. Disconnect the computer 14-pin connector.
3. Connect a voltmeter to terminal "12" in the 14-pin connector and ground. (Scheme 79) Turn the ignition switch to the "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. (Scheme 79): Checking 14-Pin Terminal No. 12 To Ground
4. If voltage is okay, check terminal in terminal "12" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If voltage is not okay, repair wire to terminal "12" for an open circuit to the O2 solenoid.
5. If voltmeter reading in step 2) is not pulsating, and reading is between 0-1 volt, disconnect the computer 14-pin connector. If voltage is not within 1 volt of battery voltage, replace the computer.
6. If voltage is other than specified, connect a voltmeter to the Red wire of the harness connector (2-pin connector on 4-cylinder and 4-pin connector on V8 models) and ground. (Scheme 80) Turn the ignition switch to the "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. (Scheme 80): Checking Oxygen Sensor Circuit
7. If voltage is okay, repair O2 solenoid-to-computer (Green wire) for a short circuit to ground. If zero volts, repair Red wire for an open circuit to the ignition switch.

Scheme 81

Scheme 82

Scheme 83

Scheme 84

Scheme 85

1. Connect diagnostic read-out box to the engine harness connector. Connect a voltmeter to the Orange wire in terminal "5" of the transmission unlock relay and ground. (Scheme 81) Place system in ATM Test Mode 92. Voltmeter reading should be pulsating between 2-10 volts. (Scheme 81): Transmission Unlock Relay Terminal No. 5 To Ground
2. If voltmeter reading is not pulsating, but reads within 1 volt of battery voltage, turn ignition off. Disconnect the computer 14-pin connector. Connect a voltmeter to the connector terminal "3" and ground. (Scheme 82) Turn the ignition switch to the "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. (Scheme 82): 14-Pin Terminal No. 3 To Ground
3. If voltage is okay, check terminal in terminal "3" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If voltage is not okay, repair wire in terminal "3" for an open circuit to the transmission unlock relay.
4. If voltmeter reading in step 1) is pulsating between 0 and 2 volts, connect a jumper wire between terminals "1" and "2" of the transmission unlock relay. (Scheme 83) The relay should cycle on and off. (Scheme 83): Transmission Unlock Relay Terminal Nos. 1 & 2
5. If the relay does not cycle on and off, replace the relay. If the relay cycles on and off, repair wire from terminal "2" of the transmission unlock relay to the wiring harness splice for an open circuit.
6. If the voltmeter reading in step 1) pulsates once between 2-10 volts, then stays within 1 volt of battery voltage and relay clicks once, turn ignition off. Connect a jumper wire from the relay mounting bracket to ground. (Scheme 84) Place system in ATM Test Mode 92. Voltmeter reading should be pulsating between 2-10 volts and the relay should be clicking. (Scheme 84): Transmission Unlock Relay Ground Check
7. If voltmeter pulsates once between 2-10 volts, and then stays within 1 volt of battery voltage and the relay clicks once, replace the relay. If voltmeter reading pulsates between 2-10 volts and the relay is clicking, repair the relay ground.
8. If voltmeter reading in step 1) is not pulsating, but reads 0-1 volt, disconnect computer 14-pin connector. Connect voltmeter to terminal "5" (Orange wire) of the transmission unlock relay and ground. (Scheme 85) Voltmeter reading should be within 1 volt of battery voltage. (Scheme 85): Transmission Unlock Relay Terminal No. 5 To Ground
9. If voltage is within 1 volt of battery voltage, replace the computer. If voltage is not within 1 volt of battery voltage, repair Orange wire to connector terminal "5" or the relay for a short to ground.

Scheme 86

Scheme 87

1. Connect diagnostic read-out box to the engine harness connector. Connect voltmeter to the air switching solenoid connector (Green wire) and ground. (Scheme 86) Place system in ATM Test Mode 93. Voltmeter reading should be pulsating and the solenoid should be clicking. (Scheme 86): Air Switching Solenoid Circuit Check
2. If voltmeter reading is pulsating between 0-2 volts, replace the dual solenoid assembly. If voltmeter reading is not pulsating, but reads within 1 volt of battery voltage, turn ignition off. Disconnect the computer 14-pin connector. Connect voltmeter to connector terminal "13" and ground. (Scheme 87) Turn the ignition switch to the "RUN" position. (Scheme 87): 14-Pin Terminal No. 13 To Ground
3. Voltmeter reading should be within 1 volt of battery voltage. If voltage is okay, check terminal in terminal "13" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If voltage is not okay, repair wire in terminal "13" for an open circuit to the air switching control solenoid.
4. If voltmeter reading in step 2) is not pulsating, but reads 0-1 volt, disconnect the computer 14-pin connector. Connect voltmeter to the air switching solenoid connector (Green wire) and ground. (Scheme 88) Voltmeter reading should be within 1 volt of battery voltage. If voltage is within 1 volt of battery voltage, replace the computer. If voltage is not within 1 volt of battery voltage, repair wire in terminal "13" for a short to ground.

Air Switching Solenoid Circuit Check. Scheme 88

Scheme 89

Scheme 90

1. Connect diagnostic read-out box to the engine harness connector. Connect voltmeter to the carburetor connector (Green/White wire) and ground (3-pin connector on 6-cylinder and 4-pin connector on V8 models). (Scheme 89) Place fast idle speed adjusting screw on the highest step of the fast idle cam. (Scheme 89): Carburetor Connector Identification
2. Lightly press on the throttle control solenoid plunger with your finger. Place system in ATM Test Mode 97. Voltmeter reading should be pulsating and solenoid plunger should move in and out. If voltmeter pulsates, but solenoid plunger does not move, replace the solenoid.
3. If voltmeter reading does not pulsate, turn ignition off. Disconnect the computer 14-pin connector. Disconnect the carburetor connector (3-pin connector on 6-cylinder and 4-pin connector on V8 models). Connect an ohmmeter between 14-pin connector terminal "6" and the carburetor harness connector (Green/White wire). (Scheme 90) (Scheme 90): Checking 14-Pin Terminal No. 6 To Carburetor
4. Ohmmeter should show continuity. If there is continuity, check terminal in terminal "6" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If no continuity, repair the wire to terminal "6" for an open circuit.

Scheme 91

Scheme 92

1. Connect diagnostic read-out box to the engine harness connector. Connect a voltmeter to the solenoid 3-pin connector (Gray wire) and ground. (Scheme 91) Place system in ATM Test Mode 98. Voltmeter reading should be pulsating and solenoid should be clicking. If voltmeter pulsates between 0-2 volts, replace the dual solenoid assembly. (Scheme 91): EGR Or Canister Purge Solenoid Circuit
2. If voltmeter is not pulsating, but reads within 1 volt of battery voltage, turn ignition off. Disconnect the computer 14-pin connector. Connect voltmeter to 14-pin connector terminal "8" and ground. (Scheme 92) Turn ignition switch to the "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. (Scheme 92): 14-Pin Terminal No. 8 To Ground
3. If voltage is okay, check terminal in terminal "8" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If voltage is not okay, repair wire to terminal "8" for an open circuit to the control solenoid.
4. If voltmeter is not pulsating, but reads 0-1 volt, disconnect the computer 14-pin connector. Voltmeter reading should be within 1 volt of battery voltage. If voltage is within 1 volt of battery voltage, replace the computer. If voltage is not within 1 volt of battery voltage, repair the wire to terminal "8" for a short to ground.

Scheme 93

Scheme 94

Scheme 95

1. Turn ignition off. Connect voltmeter to the O2 solenoid (Green wire) at the carburetor connector (3-pin connector on 6-cylinder and 4-pin connector on V8 models). (Scheme 95) Disconnect and plug the vacuum hose at the computer. Connect a hand vacuum pump to the computer and apply 14 in. Hg vacuum. Connect a tachometer.
2. Disconnect the O2 sensor connector. Start the engine and idle for 1 minute. Raise the engine speed to 2000 RPM. Hold the O2 sensor harness terminal with one hand and touch the battery positive terminal with the other hand. (Scheme 93) Voltmeter reading should decrease toward zero volts. (Scheme 93): Oxygen Sensor Connector To Battery Check
3. If voltage does not decrease, return engine to idle. Turn ignition off. Disconnect the computer 14-pin connector. Connect an ohmmeter between the harness end of the O2 sensor connector and the 14-pin connector terminal "10". (Scheme 94) Ohmmeter should show continuity. (Scheme 94): O2 Sensor Harness Connector To 14-Pin Terminal No. 10
4. If there is continuity, check terminal in terminal "10" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If no continuity, repair the wire for an open circuit.
5. If voltage reading in step 2) decreases, reconnect O2 sensor connector. Wait a few seconds for the O2 feedback system to start working. Voltmeter reading should be pulsating between 7-14 volts. If voltage reading is okay, remove the air cleaner cover. Slowly close the choke plate. (Scheme 95): Oxygen Sensor Circuit Check
6. Voltmeter reading should decrease toward zero volts. If voltage drops, O2 feedback system is okay. Proceed to DR19. If voltmeter reading does not decrease, check O2 sensor wire for an open circuit to the 14-pin connector terminal "10". Repair circuit if open. If there is no open circuit, replace O2 sensor.
7. If voltage in step 2) is below 7 volts, disconnect the hose from the PCV valve and cover it with your finger. Slowly move your finger to allow more air to enter the hose. Voltmeter reading should increase toward 14 volts. If voltage increases, O2 feedback system is okay. Proceed to DR19. If voltage does not increase, replace the O2 sensor.

Scheme 96

Scheme 97

Scheme 98

1. Disconnect the center terminal connector from the charge temperature switch. Connect voltmeter to the disconnected wire and ground. (Scheme 96) Turn the ignition switch to the "RUN" position. Voltmeter should show voltage. NOTE: The amount of voltage is not important, as long as there is voltage. (Scheme 96): Charge Temperature Switch Voltage Test
2. If there is voltage, disconnect the side terminal connector from the charge temperature switch. Connect an ohmmeter between the side terminal connector wire and ground. (Scheme 97) Ohmmeter should show continuity. If there is continuity, replace the charge temperature switch. If there is no continuity, repair wire for an open circuit. (Scheme 97): Charge Temperature Switch Resistance Check
3. If there is no voltage in step 1), turn the ignition off. Disconnect the computer 14-pin connector. Connect an ohmmeter between the charge temperature switch center wire connector and 14-pin connector terminal "9". (Scheme 98) Ohmmeter should show continuity. (Scheme 98): 14-Pin Terminal No. 9 To Charge Temperature Switch
4. If there is continuity, check terminal in terminal "9" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If there is no continuity, repair wire in terminal "9" for an open circuit.

Scheme 99

Scheme 100

1. Connect diagnostic read-out box to the engine harness connector. Disconnect both connectors from the charge temperature switch. (Scheme 99) Place the system in Sensor Test Mode 93. Display on the read-out box should be "03". If "03" is not displayed on the read-out box, check terminal in 14-pin connector terminal "9" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. (Scheme 99): Charge Temperature Switch Connectors
2. If "03" is displayed, connect the Tan wire to the Black wire with a jumper lead. (Scheme 100) Read-out box display should change from "03" to "01" after jumper lead is connected. If the display changes from 03 to 01, replace the charge temperature switch. (Scheme 100): Installing Jumper Wire On Charge Temperature Switch
3. If the display does not change, connect the Tan wire to ground using a jumper lead. Read-out box display should change from "03" to "01" after jumper lead is connected. If display changes from "03" to "01", repair the Black wire for an open circuit. If the display does not change, repair the Tan wire for an open circuit.

Installing Jumper On Charge Temperature Switch To Ground. Scheme 101

Scheme 102

Scheme 103

1. Disconnect the engine temperature sensor connector. Connect an ohmmeter between the terminals of the sensor. (Scheme 102) Ohmmeter reading should show resistance. NOTE: The amount of resistance is not important. Just as long as there is resistance. (Scheme 102): Engine Temperature Sensor Temperature
2. If there is zero resistance or an open circuit, replace the sensor. If there is resistance, reconnect the engine temperature sensor connectors. Connect an ohmmeter between 10-pin connector terminal "9" and 14-pin connector terminal "11". (Scheme 103) Ohmmeter should show resistance. NOTE: The amount of resistance is not important, only that there is resistance. (Scheme 103): 14-Pin Terminal No. 11 & 10-Pin Terminal No. 9
3. If there is resistance, check terminal in 14-pin connector terminal "11" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If there is an open circuit, repair wire to 14-pin connector terminal "11".

Scheme 104

Scheme 105

1. Connect diagnostic read-out box to the engine harness connector. Disconnect coolant sensor harness connector. (Scheme 104) Read-out box display should read "01". If display does not read "01", replace the computer. (Scheme 104): Engine Temperature Sensor Connector Identification
2. If display reads "01", place system in Sensor Test Mode 92. Connect a jumper lead between coolant sensor harness connector terminals. (Scheme 105) Read-out box display should change from "01" to "03" when jumper lead is connected. If display changes from "01" to "03", replace the coolant sensor. (Scheme 105): Engine Temperature Sensor Connector With Jumper
3. If the display does not change, connect a jumper lead between the Black/Red wire and ground. (Scheme 106) Read-out box display should change from "01" to "03". If display changes from "01" to "03", repair the Black/Lt. Blue wire for an open circuit. If display does not change, repair Black/Red wire for an open circuit.

Engine Temperature Sensor Connector To Ground. Scheme 106

Scheme 107

Scheme 108

Scheme 109

1. Turn ignition off. Disconnect speed sensor from speedometer cable. Disconnect speed sensor connector. (Scheme 107) Connect an ohmmeter between the speed sensor connector terminals. Slowly rotate the speed sensor 1 revolution. The ohmmeter should show 8 pulses for every 1 revolution of the speed sensor. (Scheme 107): Speed Sensor Connector
2. If ohmmeter reading is not as specified, replace the speed sensor. If ohmmeter reading is as specified, connect voltmeter positive lead to the White/Orange speed sensor harness connector wire. Connect voltmeter negative lead to the Black/Blue speed sensor harness connector wire. (Scheme 108) (Scheme 108): Speed Sensor Harness Connector
3. Turn the ignition switch to the "RUN" position. Voltmeter reading should be at least 8.5 volts. If voltage is okay, inspect the transaxle drive gear-to-speed sensor drive gear for proper contact. If zero volts, move voltmeter negative lead to a good engine ground. If voltmeter now reads correct voltage, repair speed sensor ground wire.
4. If voltmeter still reads zero volts, turn the ignition off. Disconnect the computer 14-pin connector. Connect an ohmmeter between 14-pin connector terminal "2" and White/Orange speed sensor harness connector wire. See. (Scheme 109). Ohmmeter should show continuity. (Scheme 109): Speed Sensor Harness Connector & 14-Pin Terminal No. 2
5. If there is continuity, check terminal in terminal "2" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If there is no continuity, repair open circuit in White/Orange wire.

Scheme 110

Scheme 111

Scheme 112

1. Connect diagnostic read-out box to the engine harness connector. Disconnect the speed sensor connector. (Scheme 110) Place system in Sensor Test Mode 96. Read-out box display should read "02". If the display does not read "02", replace the computer. (Scheme 110): Speed Sensor Connector Identification
2. If the display reads "02", connect a jumper lead between speed sensor connector terminals on the engine harness. (Scheme 111) Read-out box display should change from "02" to "01". (Scheme 111): Speed Sensor Harness Connector Terminal Jumper Wire
3. If display does not change, connect a jumper lead between speed sensor harness connector White wire and a good engine ground. (Scheme 112) Read-out box display should change from "02" to "01". If the display changes, repair the Black wire of the speed sensor harness connector for an open circuit. (Scheme 112): Speed Sensor Harness Connector Jumper Wire To Ground
4. If display does not change from "02" to "01", repair the White wire of the speed sensor harness connector for an open circuit. If the display changed from "02" to "01" in step 2) turn the ignition off. Remove the speed sensor from the transmission.
5. Connect an ohmmeter between the speed sensor harness connector terminals. (Scheme 113) Slowly rotate the speed sensor 1 revolution. The ohmmeter should show 8 pulses for every 1 revolution of the speed sensor. If ohmmeter reading is okay, inspect transmission drive gear and speedometer cable. If ohmmeter reading is not okay, replace the speed sensor.

Speed Sensor Pulse Check. Scheme 113

Scheme 114

Scheme 115

Scheme 116

1. Disconnect diagnostic read-out box from the engine harness connector. Connect a voltmeter to the diagnostic connector terminal "4" and ground. (Scheme 114) Turn the ignition switch to the "RUN" position. Voltmeter reading should be 4-5 volts. (Scheme 114): Diagnostic Connector Terminal Identification
2. If voltage is okay, turn ignition off. Disconnect the 14-pin connector from the computer. Connect an ohmmeter between engine harness diagnostic connector terminal "2" and the computer 14-pin connector terminal "14". Ohmmeter should show continuity. (Scheme 115): 14-Pin Terminal 14 To Diagnostic Connector Terminal 2
3. If no continuity, repair wire to connector terminal "14" for an open circuit to the engine harness connector. If there is continuity, check terminal in terminal "14" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer.
4. If voltage in step 1) was not as specified, turn ignition off. Disconnect the 14-pin connector from the computer. Connect an ohmmeter between engine harness connector terminal "4" and the computer 14-pin connector terminal "1". Ohmmeter should show continuity. (Scheme 116): 14-Pin Terminal 1 To Diagnostic Connector Terminal 4
5. If no continuity, repair wire to connector terminal "1" for an open circuit to the engine harness connector. If there is continuity, check terminal in terminal "1" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer.

DR12 - FAST IDLE CAM LINKAGE & CHOKE CHECK

Note. Engine must be cold to perform this test.

Scheme 117

1. Press the accelerator linkage to the proper start position to set the choke. Remove the air cleaner. Ensure the choke plate and fast idle cam are in their proper position. Choke plate should be fully closed and the fast idle screw should be positioned on the highest step of the fast idle cam. (Scheme 117) (Scheme 117): Carburetor Choke Plate Closed
2. If choke and cam position are okay, proceed to DR13. If choke is not fully closed or cam is not in position, check for sticking or binding choke plate. Repair choke and linkage as necessary.

DR13 - CHOKE VACUUM KICK CHECK

Note. Engine must be cold to perform this test.

Scheme 118

1. Remove air cleaner assembly. Position the fast idle screw on the highest step of the fast idle cam. Remove the vacuum hose from the choke diaphragm. Connect a vacuum pump to the choke diaphragm and apply 15 in. Hg vacuum. Measure clearance between top of choke plate and air horn wall. (Scheme 118) (Scheme 118): Choke Vacuum Kick Check
2. Vacuum should remain at 15 in. Hg and choke plate should open to proper vacuum kick specification. If vacuum remains at 15 in. Hg and choke plate opens to specification, proceed to DR14. If necessary, adjust vacuum kick to specifications. If diaphragm does not hold vacuum, replace diaphragm.

DR14 - HEATED AIR INTAKE SYSTEM CHECK

Note. Engine must be cold to perform this test.

Scheme 119

1. Disconnect air duct from the air cleaner snorkel. Disconnect vacuum supply hose to the heated air intake system air temperature sensor. Apply a minimum of 15 in. Hg vacuum. (Scheme 119) Vacuum should build up to 15 in. Hg and close the heated air door when temperature is below 70°F (21°C). The vacuum should then slowly bleed down, opening the heated air door. (Scheme 119): Applying Vacuum To Air Temperature Sensor NOTE: The 3.7L engine uses a vacuum delay valve at the heated air door diaphragm. This delays the opening of the heated air door when vacuum bleeds off.
2. If vacuum builds up, closes the heated air door and then bleeds down, proceed to DR15. If vacuum builds up, but does not open the heated air door, repair or replace heated air door as necessary.
3. If vacuum does not build up or does not bleed down, replace the air temperature sensor. If vacuum builds up and bleeds down, but heated air door does not open, repair or replace heated air door as necessary.

Fed. 3.7L With A/T & Fed. 5.2L

1. Connect diagnostic read-out box to the engine harness connector. Place the system in Sensor Test Mode 92. Read-out box display should read as shown in the «COOLANT SENSOR CALIBRATION - FED»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) . 3.7L WITH A/T & FED. 5.2L table.
2. If display code is okay, proceed to DR16. If display code is not okay, replace coolant sensor.

COOLANT SENSOR CALIBRATION - FED. 3.7L WITH A/T & FED. 5.2L

All Models (Except Fed. 3.7L With A/T & Fed. 5.2L)

1. Disconnect coolant sensor connector. Connect an ohmmeter between coolant sensor terminals. (Scheme 120) Ohmmeter reading should be as shown in «COOLANT SENSOR CALIBRATION - ALL OTHERS»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) table.
2. If resistance is within specifications, proceed to DR16. If resistance is not within specifications, replace coolant sensor.

Checking Engine Temperature Sensor Resistance. Scheme 120

COOLANT SENSOR CALIBRATION - ALL OTHERS

DR16 - EGR OR CANISTER PURGE CVSCC VALVE CHECK

Note. Engine must be cold to perform this test.

1. Disconnect the CVSCC valve vacuum hoses. Connect a hand vacuum pump to either vacuum port on the valve. (Scheme 121) Apply a minimum of 10 in. Hg vacuum. Vacuum should hold on a cold engine, below specified opening temperature. See «CVSCC VALVE OPENING SPECIFICATION»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart.
2. If valve holds vacuum as specified, proceed to DR17. If valve does not hold vacuum, replace CVSCC valve.

CVSCC Valve. Scheme 121

CVSCC VALVE OPENING SPECIFICATION

DR17 - CHOKE POSITION WITH ENGINE RUNNING CHECK

Note. Engine must be cold to perform this test.

Scheme 122

Scheme 123

Scheme 124

Scheme 125

Scheme 126

Scheme 127

1. Start engine. Observe choke plate position. (Scheme 122) Choke plate should open slightly from the fully closed position. If choke plate opens, connect voltmeter to choke control switch terminal that is connected to the choke heater and ground. (Scheme 123) (Scheme 122): Choke Plate Position
2. With air temperature below 55°F (13°C), voltmeter reading should be zero volts with a single stage choke control and 5-9 volts with a dual stage choke control. With air temperature above 80°F (27°C), voltmeter reading should be within 1 volt of battery voltage with both types of choke control. (Scheme 123): Voltmeter To Choke Control Switch & Ground NOTE: Dual stage choke controls have an external resistor, while single stage choke controls do not.
3. If voltage reading is within specifications, turn ignition off. Disconnect wire from choke control that goes to the electric choke heater. Connect an ohmmeter between the choke heater wire and the choke heating element retaining screw. (Scheme 124) Ohmmeter reading should be 4-12 ohms of resistance. If resistance is not within specification, replace choke heating element. (Scheme 124): Checking Choke Heater Resistance
4. If resistance is within specification, proceed to DR18. If voltmeter reading in step 2) is not within specifications, connect voltmeter to ignition feed wire connector of the choke control switch and ground. (Scheme 125) Voltmeter reading should be within 1 volt of battery voltage. (Scheme 125): Voltmeter To Choke Control Switch & Ground
5. If voltage is within specifications, replace choke control unit. If voltage is not within specifications, turn ignition off. Disconnect oil pressure switch connector. Connect voltmeter to engine harness connector at oil pressure switch terminal "A" and ground. (Scheme 126) (Scheme 126): Oil Pressure Switch Engine Harness Connector Identification
6. Turn ignition switch to the "RUN" position. Voltage should be within 1 volt of battery voltage. If voltage is not within specification, repair harness to ignition switch for an open circuit. If voltage is within specification, turn ignition off. Disconnect ignition feed wire from choke control switch.
7. Connect an ohmmeter between the engine harness connector at the oil pressure switch terminal "C" and choke control switch wire. (Scheme 127) Ohmmeter should show continuity. If there is continuity, replace oil pressure switch. If there is no continuity, repair harness for an open circuit. (Scheme 127): Checking Resistance To Choke Control Switch
8. If choke plate did not open in step 1), disconnect vacuum hose to the choke vacuum kick diaphragm and connect a vacuum gauge. (Scheme 128) Start engine. Vacuum gauge reading should be manifold vacuum. If vacuum is okay, repair choke linkage. If vacuum is not okay, check vacuum source from the carburetor.

Installing Vacuum Gauge. Scheme 128

DR18 - FUEL FOULED SPARK PLUGS CHECK

Remove spark plugs. Inspect spark plug tips for wet fuel. Spark plugs should be dry. If spark plugs are dry, proceed to DR26 - BOWL VENT SYSTEM CHECK . If spark plugs are wet with fuel, clean and reinstall. Check for fuel in crankcase. Change oil and filter if necessary.

Scheme 129

1. With engine at normal operating temperature, disconnect computer 10-pin connector. Connect an ohmmeter between the 10-pin connector terminal "7" and ground. (Scheme 129) Open and close the throttle while watching the ohmmeter. Ohmmeter reading should show continuity, with no resistance, when the throttle is closed and should show no continuity when the throttle is open. (Scheme 129): 10-Pin Terminal No. 7 To Ground
2. If there is continuity when the throttle is open, repair wire to connector terminal "7" for a short to ground. If there is continuity with resistance when the throttle is closed, check and clean the carburetor switch for corrosion.
3. If there is no continuity when the throttle is closed, repair wire to connector terminal "7" for an open circuit to the carburetor switch. If continuity checks okay, proceed to «DR20 - ENGINE TEMPERATURE SENSOR CALIBRATION CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).

Fed. 3.7L With A/T & Fed. 5.2L Models

1. With engine at normal operating temperature, connect the diagnostic read-out box to the engine harness connector. Place the system in Sensor Test Mode 92. Read-out box display should read as shown in the «COOLANT SENSOR CALIBRATION - FED»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) . 3.7L WITH A/T & FED. 5.2L chart.
2. If display code is okay, proceed to «DR21 - CHOKE POSITION CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) . If display code is not okay, replace coolant sensor.

Diagnostic Read-Out Box. Scheme 130

All Models (Except Fed. 3.7L With A/T & Fed. 5.2L Models)

With engine at normal operating temperature, disconnect the engine temperature sensor. Connect an ohmmeter between the sensor terminals. (Scheme 131) Ohmmeter reading should be 176-3900 ohms. If resistance is not okay, replace sensor. If resistance is okay, proceed to DR21 - CHOKE POSITION CHECK.

Checking Engine Temperature Sensor Resistance. Scheme 131

Scheme 132

Scheme 133

Scheme 134

Scheme 135

Scheme 136

1. With engine at normal operating temperature, remove air cleaner assembly. Start engine and check choke position. (Scheme 132) Choke plate should be fully open. If choke plate is fully open, proceed to «DR22 - EGR SYSTEM CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system). If choke plate is not fully open, connect a voltmeter to choke control switch terminal that is connected to the choke heater and ground. (Scheme 133) (Scheme 132): Choke Position Check
2. With air temperature below 55°F (13°C), voltmeter reading should be zero volts with a single stage choke control and 5-9 volts with a dual stage choke control. With air temperature above 80°F (27°C), voltmeter reading should be within 1 volt of battery voltage with both types of choke control. (Scheme 133): Choke Control Switch To Ground Check NOTE: Dual stage choke controls have an external resistor, while single stage choke controls do not.
3. If voltage reading is within specifications, turn ignition off. Disconnect wire from choke control that goes to the electric choke heater. Connect an ohmmeter between the choke heater wire and the choke heating element retaining screw. (Scheme 134) Ohmmeter reading should be 4-12 ohms of resistance. If resistance is not within specification, replace choke heating element. (Scheme 134): Choke Heater Resistance Check
4. If resistance is within specification, repair or replace choke linkage. If voltmeter reading in step 2) is not within specifications, connect voltmeter to ignition feed wire connector of the choke control switch and ground. (Scheme 135) Voltmeter reading should be within 1 volt of battery voltage. (Scheme 135): Choke Control Switch Ignition Feed Check
5. If voltage is within specifications, replace choke control unit. If voltage is not within specifications, turn ignition off. Disconnect oil pressure switch connector. Connect voltmeter to engine harness connector at oil pressure switch terminal "A" and ground. (Scheme 136) (Scheme 136): Oil Pressure Switch Engine Harness Connector To Ground Check
6. Turn ignition switch to the "RUN" position. Voltage should be within 1 volt of battery voltage. If voltage is not within specification, repair harness to ignition switch for an open circuit. If voltage is within specification, turn ignition off. Disconnect ignition feed wire from choke control switch.
7. Connect an ohmmeter between the engine harness connector at the oil pressure switch terminal "C" and choke control switch wire. (Scheme 137) Ohmmeter should show continuity. If there is continuity, replace oil pressure switch. If no continuity, repair harness for an open circuit.

Engine Harness Connector Terminal C To Choke Control Check. Scheme 137

Scheme 138

Scheme 139

Scheme 140

Scheme 141

Scheme 142

Scheme 143

Scheme 144

Scheme 145

1. With engine at normal operating temperature, let engine idle for 1 minute. While observing EGR valve stem, raise engine speed to more than 2500 RPM for more than 5 seconds. (Scheme 138) As engine speed increases, the EGR valve stem should move upward. (Scheme 138): EGR Valve Identification
2. If EGR valve stem moves upward, return engine to idle speed. Connect a tachometer. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve. (Scheme 139) Very slowly apply vacuum to EGR valve. Engine RPM should drop when 3-5 in. Hg vacuum is applied and continue to drop as more vacuum is applied. (Scheme 139): Connecting Vacuum Pump to Valve
3. If engine speed drops, proceed to DR23 for all models except Fed. 5.2L. On Fed. 5.2L models, proceed to DR24. If engine speed does not drop, or engine speed does not drop until 5 in. Hg vacuum or more is applied, replace EGR valve.
4. If the EGR valve stem in step 1) did not move, disconnect and plug vacuum hose at solenoid kicker, if equipped. Run engine at idle for more than 2 minutes. Connect vacuum gauge to EGR vacuum hose. (Scheme 140) Slowly increase engine speed. Vacuum reading should increase as engine speed increases. (Scheme 140): Connecting Vacuum Gauge To EGR Hose NOTE: Federal 5.2L engines use a vacuum delay valve in the EGR hose.
5. If vacuum reading is okay, replace the EGR valve. If vacuum reading is not okay, on all models except Federal 5.2L, disconnect lower hose from EGR solenoid and connect a vacuum gauge to the solenoid. (Scheme 141) Slowly increase engine speed. Vacuum reading should increase as engine speed increases. If vacuum reading is okay, repair vacuum hose to EGR valve. (Scheme 141): Connecting Vacuum Gauge To Solenoid
6. If vacuum reading is not okay, reconnect lower hose to solenoid. Disconnect upper hose from EGR solenoid and connect a vacuum gauge to the solenoid. (Scheme 142) Slowly increase engine speed. Vacuum reading should increase as engine speed increases. If vacuum reading is not okay, repair vacuum supply from carburetor. (Scheme 142): Connecting Vacuum Gauge To Upper Solenoid Hose
7. If vacuum reading is okay, reconnect vacuum hose to solenoid. Disconnect vacuum hose connector from EGR amplifier. Connect vacuum gauge to vacuum hose connector terminal "2". (Scheme 143) Slowly increase engine speed. Vacuum reading should increase as engine speed increases. If vacuum reading is not okay, repair vacuum supply from carburetor. (Scheme 143): EGR Amplifier Hose 2 Location
8. If vacuum reading is okay, connect vacuum gauge to vacuum hose connector terminal "1" (top of connector). (Scheme 144) Vacuum gauge reading should be manifold vacuum. If vacuum reading is okay, replace EGR amplifier. If vacuum reading is not okay, repair vacuum supply from intake manifold. (Scheme 144): EGR Amplifier Hose 1 Location
9. If vacuum reading in step 5) is not okay, on Federal 5.2L models, disconnect vacuum hose connector to CVSCC valve and connect a vacuum gauge to the hose from the carburetor. (Scheme 145) Slowly increase engine speed. Vacuum reading should increase as engine speed increases. If vacuum reading is not okay, repair vacuum supply from carburetor. (Scheme 145): Connecting Vacuum Gauge To CVSCC Valve Hose
10. If vacuum reading is okay, connect a vacuum pump to either port of the CVSCC valve. (Scheme 146) Apply vacuum. Valve should not hold vacuum. If valve does not hold vacuum, repair vacuum hose to EGR valve. Ensure vacuum delay valve is operating properly. If CVSCC valve holds vacuum, replace the valve.

Connecting Vacuum Pump To CVSCC Valve. Scheme 146

DR23 - CANISTER PURGE SYSTEM CVSCC VALVE CHECK

With engine at normal operating temperature, disconnect vacuum connector from the canister purge CVSCC valve. Connect a vacuum pump to either port of the valve. (Scheme 147) Apply vacuum. Valve should not hold vacuum. If valve does not hold vacuum, proceed to DR24. If CVSCC valve holds vacuum, replace the valve.

Connecting Vacuum Pump To CVSCC Valve. Scheme 147

Scheme 148

Scheme 149

1. With engine at normal operating temperature, disconnect the downstream air hose from the air switching valve. (Scheme 148) Start engine. Run engine for more than 2 1/2 minutes. NOTE: On Calif. 3.7L engines with manual transmission, raise engine speed to 2000 RPM. (Scheme 148): Downstream Hose Location
2. There should be air flowing from the downstream air port. If there is air flowing from port, proceed to «DR25 - HEATED AIR INTAKE SYSTEM CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__dr25-heated-air-intake-system). If there is no air flowing from port, remove upstream air hose from the air switching valve. (Scheme 149) There should be air flowing from the upstream air hose. (Scheme 149): Upstream Hose Location
3. If air is not flowing from hose, repair or replace air pump. If there is air flowing from hose, disconnect the vacuum hose from the air switching valve and connect a vacuum gauge to the hose. (Scheme 150) Vacuum reading should be zero. If vacuum reading is zero, replace air switching valve. If vacuum is not zero, replace the air switching solenoid.

Connecting Vacuum Gauge To Air Switching Valve. Scheme 150

DR25 - HEATED AIR INTAKE SYSTEM CHECK

1. With engine at normal operating temperature, disconnect the air duct from the air cleaner snorkel. Disconnect the vacuum supply hose to the heated air intake air temperature sensor. Connect a vacuum pump to the air temperature sensor and apply vacuum to sensor. (Scheme 151)
2. Sensor should not hold vacuum and heated air door should be open. If heated air door is not open, repair or replace as necessary. If sensor holds vacuum, replace sensor. If sensor does not hold vacuum and heated air door is open, proceed to «DR26 - BOWL VENT SYSTEM CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system).

Connecting Vacuum Pump To Air Temperature Sensor. Scheme 151

Scheme 152

1. With engine at normal operating temperature, remove bowl vent hose from vapor canister. Set fast idle screw on the highest step of the fast idle cam. Lightly blow into hose. Air should not flow through hose. If air flows through hose, repair bowl vent or linkage. (Scheme 152): Bowl Vent System Diagram
2. If air does not flow through hose, set throttle at curb idle position. Lightly blow into hose. Air should flow through hose. If air does not flow through hose, check for a restricted hose and/or repair bowl vent or linkage.
3. If air flows through hose, turn ignition switch to the "RUN" position. Blow into hose lightly. Air should not flow through hose. If air flows through hose, connect a voltmeter to the bowl vent solenoid wire at the carburetor connector.
4. With the key in the "RUN" position, voltage reading should be within 1 volt of battery voltage. If voltage is as specified, repair bowl vent or replace solenoid as necessary. If voltage is not as specified, repair harness for an open circuit to the ignition switch.
5. If air did not flow through hose in step 3), proceed to «DR27 - START-TO-RUN PICK-UP COIL TRANSFER CKT CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) on 3.7L automatic transmission models and «DR28 - IDLE CONTROL SOLENOID HOT RESTART CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) for all other models.

Scheme 153

Scheme 154

Scheme 155

1. Start and run engine until normal operating temperature is reached. Raise engine speed to 1100 RPM. Disconnect "Start" pick-up coil connector at the distributor. (Scheme 153) Engine should stay running. If engine stays running, proceed to «DR28 - IDLE CONTROL SOLENOID HOT RESTART CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system). (Scheme 153): Distributor Start Pick-Up Coil Connector
2. If engine stalls, disconnect the 10-pin connector from the computer. Connect an ohmmeter between 10-pin connector terminals "5" and "9". (Scheme 154) Ohmmeter reading should be 150-900 ohms. If resistance is within specifications, remove distributor cap. (Scheme 154): Checking 10-Pin Terminal No. 5 To 9
3. Measure "Run" pick-up coil air gap. (Scheme 155) Air gap should be.012" (.3 mm). Adjust air gap as necessary. If air gap is okay, check terminal in terminal "5" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. (Scheme 155): Checking Air Gap
4. If resistance in step 2) is not to specifications, disconnect "Run" pick-up coil connector. Connect an ohmmeter between the pick-up coil connector terminals. (Scheme 156) Ohmmeter reading should be 150-900 ohms. If resistance is okay, repair open circuit in harness from distributor to computer. If resistance is not within specifications, replace "Run" pick-up coil.

Run Pick-Up Coil Connector. Scheme 156

Scheme 157

Scheme 158

Scheme 159

1. With engine at normal operating temperature, remove air cleaner cover. While an assistant starts the engine, watch the idle control solenoid plunger. (Scheme 157) Slowly open the throttle. The solenoid plunger should move out and hold the throttle open for the amount of time specified in the «IDLE CONTROL SOLENOID SPECIFICATIONS»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. (Scheme 157): Idle Control Solenoid Plunger IDLE CONTROL SOLENOID SPECIFICATIONS Application Computer No. Seconds 3.7L Fed. & Hi. Alt. (1) 4289603 60 3.7L Fed. (2) 4289908 90 3.7L Calif. (1) 4289617 60 3.7L Calif. (2) 4289615 60 5.2L Fed. (1) (2) 4289982 60 5.2L Calif. (1) 4289845 25 5.2L Calif. (2) (3) 4289977 25 5.2L Calif. (2) (4) 4379236 25 5.2L Hi. Alt. (1) (2) 4289637 25 (1) Manual transmission. (2) Automatic transmission. (3) Except Ramcharger models. (4) Ramcharger models.
2. If plunger does not move, ensure the solenoid adjusting screw is not turned in all the way, preventing plunger movement; if not, replace solenoid. If vehicle is not equipped with A/C, proceed to DR29. If vehicle is equipped with A/C, run engine at idle for more than 5 minutes.
3. Turn the A/C on while watching the idle control solenoid plunger. The solenoid plunger should move out and open the throttle while the A/C compressor clutch is engaged. If plunger movement is okay, proceed to DR29. If plunger does not move, connect the diagnostic read-out box to the engine harness connector. (Scheme 158): Diagnostic Read-Out Box
4. Turn A/C off. Place the system in the Switch Test Mode. Press the A/C button on and off. Code "88" should appear on the read-out box display when the A/C button is pressed on and then return to "00" when turned off. If Code "88" appears when the A/C is turned on, replace the computer.
5. If Code "88" does not appear, turn the ignition off. Disconnect the computer 14-pin connector. Connect a voltmeter to 14-pin connector terminal "7" and ground. (Scheme 159) Turn the A/C off. Turn the ignition switch to the "RUN" position. Voltmeter reading should be within 1 volt of battery voltage. (Scheme 159): Checking 14-Pin Terminal No. 7 To Ground
6. If voltage is okay, check terminal in terminal "7" to ensure it is not spread apart causing a poor connection. If connections are okay, replace computer. If voltage is not okay, repair open circuit in wire from connector terminal "7" to the A/C switch.

DR29 - SECONDARY IGNITION SYSTEM CHECK

Turn all lights and accessories off. With engine at normal operating temperature, connect a suitable engine analyzer to the engine. Start engine and let engine speed stabilize for 2 minutes. Check secondary ignition pattern. Check ignition coil output. Open circuit secondary ignition voltage should be at least 25,000 volts.

Scheme 160

Scheme 161

Scheme 162

Scheme 163

1. Connect a tachometer and timing light to the engine. Ground the carburetor switch. Start and run the engine until normal operating temperature is reached. Raise engine speed to more than 1100 RPM. Disconnect and plug vacuum hose to the computer. NOTE: Engine RPM will drop on California and High Altitude 5.2L models when the vacuum hose to the computer is disconnected.
2. Engine speed should be within specifications when setting timing. See «TIMING RPM SPECIFICATIONS»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. Adjust idle speed to specifications before setting timing. (Scheme 160): Ignition Timing Marks TIMING RPM SPECIFICATIONS Application Timing RPM 3.7L Federal 500-800 Calif. 500-900 5.2L Federal 600-800 Calif. 550-750 High Alt. 550-750
3. Basic timing should be within 2° of specification shown on vehicle emission label. Adjust timing if not within specifications. Remove jumper lead from carburetor ground switch. Connect a vacuum pump to the computer. (Scheme 161) Apply 16 in. Hg vacuum. Raise engine speed to 2000 RPM. Timing should be within 4° of specification. See «SPARK ADVANCE SPECIFICATIONS»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. (Scheme 161): Connecting Vacuum Pump To Computer SPARK ADVANCE SPECIFICATIONS Application Computer No. Spark Advance 3.7L Fed. & High Alt. (1) 4289603 33 Federal (2) 4289908 38 Calif. (1) 4289617 30 Calif. (2) 4289615 30 5.2L Federal (1) (2) 4289982 45 Calif. (1) 4289845 34 Calif. (2) (3) 4289977 45 Calif. (2) (4) 4379236 42 High Alt. (1) (2) 4289637 34 (1) Manual transmission. (2) Automatic transmission. (3) Except Ramcharger models. (4) Ramcharger models.
4. If spark advance is not within specifications, replace the computer. If spark advance is okay, return engine to idle. Disconnect vacuum pump from the computer. Connect a vacuum gauge to the computer vacuum supply hose. (Scheme 162) Gauge should read manifold vacuum. If vacuum reading is not okay, check and repair vacuum supply from carburetor. (Scheme 162): Connecting Vacuum Gauge To Supply Hose
5. On all models except Federal 3.7L with auto. trans. and Federal 5.2L, proceed to «DR31 - IDLE RPM CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__dr31-idle-rpm-check). On Federal 3.7L with automatic transmission and Federal 5.2L models, connect diagnostic read-out box to the engine harness connector. Place the system in Sensor Test Mode 91. Connect vacuum pump to the computer. (Scheme 163) (Scheme 163): Connecting Vacuum Pump To Computer
6. Diagnostic read-out box should display "01" when 0-5 in. Hg vacuum is applied to the computer, "02" when 5-15 in. Hg vacuum is applied and "03" when more than 15 in. Hg vacuum is applied. If display codes on diagnostic read-out box are correct, proceed to «DR31 - IDLE RPM CHECK»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system__dr31-idle-rpm-check). If display codes are incorrect, replace the computer.

DR31 - IDLE RPM CHECK

1. Turn all lights and accessories off. Place transmission in neutral or park. Set parking brake. Start and run the engine until normal operating temperature is reached. Ground the carburetor switch with a jumper wire. Disconnect and plug vacuum hose at the computer. Disconnect and plug vacuum hose from the EGR valve.
2. Disconnect and plug 3/16" vacuum hose from vapor canister. Remove PCV valve from the valve cover and allow it to draw outside air. On vehicles with oxygen feedback system, disconnect and ground O2 sensor wire. Run the engine for 4 minutes before proceeding. Tachometer reading should be within specifications.
3. Set idle RPM to specifications as necessary. Tee in propane supply into the choke vacuum kick diaphragm vacuum hose. Open propane valve and meter in propane until maximum RPM is obtained. Engine speed should be increased as shown in the «PROPANE ENRICHED IDLE SPEED»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. Set propane enriched idle speed to specifications as necessary. PROPANE ENRICHED IDLE SPEED (1) Application RPM Increase 3.7L Federal 25 3.7L California M/T 75 A/T 50 5.2L Federal Except High Alt. 50 5.2L High Alt. Kit 70 5.2L Calif. M/T 50 A/T 90 High Alt. 60 (1) All specifications are plus or minus 50 RPM.
4. Open throttle and position fast idle adjusting screw on the 2nd highest step of the fast idle cam. Fast idle speed should be set to specifications +/- 100 RPM. See «FAST IDLE SPEED»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. Adjust fast idle speed to specifications as necessary. FAST IDLE SPEED Application Carb. No. Specification 3.7L 4306459 1600 3.7L 4306460 1600 3.7L 4306461 1600 3.7L 4306462 1600 5.2L 4324629 (1) 1550 5.2L 4324633 1450 5.2L 4324632 1400 (1) Add 50 RPM for High Alt. models.
5. Energize the solenoid by turning on the A/C and disconnecting the compressor clutch, or connect a jumper lead between the positive battery terminal and the solenoid feed wire. Solenoid idle speed should be set to specifications. See «SOLENOID IDLE SPEED»(/dodge/ram-van/ii-1979-1993/remont/testing-diagnostics/#37l-52l-efc-system) chart. Adjust solenoid idle speed as necessary.

SOLENOID IDLE SPEED

DR32 - SYSTEM & COMPONENT CHECKING

At this point, test procedures have determined that all engine control systems are operating correctly and are not the cause of the driveability problem. Check the following as possible causes

1. Check for at least 13 in. Hg engine vacuum in Neutral.
2. Check engine valve timing.
3. Check engine compression.
4. Check engine cooling system.
5. Check exhaust system for restrictions.
6. Check power heat riser valve for vacuum below 145°F (63°C).
7. Check engine PCV system for free flow.
8. Check intake manifold heat crossover for plugging.
9. Check torque converter stall speed.
10. Check power brake booster for internal vacuum leaks.
11. Check for fuel contamination.
12. Check carburetor for circuit contamination and proper calibration.
13. Check Technical Service Bulletins that may apply to vehicle.

Removal

1. Remove negative battery terminal. Disconnect 10-pin and 14-pin connectors from computer. Remove vacuum hose from vacuum transducer. Remove mounting screws from inside air cleaner and remove computer.
2. DO NOT remove grease from harness connectors or connector terminals in computer. Grease is used to prevent moisture from corroding terminals.

Installation

If there is not at least 1/2" of grease on bottom of computer connector terminals, apply a liberal amount of multipurpose grease (Mopar No. 2932524 ) over entire end of plug before reinstalling. Reverse removal procedure to complete installation.

Note. Computer is not serviceable. DO NOT attempt to take it apart for any reason. If vacuum transducer is defective, entire computer must be replaced.

Removal & Installation

Remove bracket and switch assembly from carburetor. Disconnect electrical connector. To install, reverse removal procedure and adjust if necessary.

Disconnect battery cable and electrical lead at sensor. Remove sensor. If old sensor is to be reinstalled, coat threads with anti-seize compound. New sensors are manufactured with compound already applied. Hand start sensor, then tighten to 20 ft. lb. (27 N.m). Connect electrical connector and battery cable.

Wiring Diagram for RWD Truck EFC System. Scheme 164

Wiring Diagram for RWD Van EFC System. Scheme 165

See also:
• NS2 - CHECKING FOR FUEL IN CARBURETOR
• NS5 - IGNITION COIL SPARK CHECK
• NS3 - FUEL FOULED SPARK PLUGS CHECK
• NS4 - ENGINE TIMING CHECK
• NS6C - DISTRIBUTOR DUAL PICK-UP COIL RESISTANCE CHECK
• DR1D - INTERMITTENT FAILURE
• DR12 - FAST IDLE CAM LINKAGE & CHOKE CHECK
• DR25 - HEATED AIR INTAKE SYSTEM CHECK
• DR31 - IDLE RPM CHECK