Engine Controls - System/component Tests - 3.9l Dodge Ram Van B1500 B pre

INTRODUCTION

Note. Testing procedures not covered in this article require a Chrysler Diagnostic Readout Box (DRB). See TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

Before testing individual components or systems, perform procedures in BASIC TESTING - 3.9L article in the ENGINE PERFORMANCE section. Since many computer controlled and monitored components set a fault message if they malfunction, also perform procedures in TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

Note. Testing of individual components does not isolate possible shorts or opens in wiring harness of electronically controlled systems. Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance unless otherwise instructed in procedure. Use an ohmmeter to isolate wiring harness shorts or opens.

Harness Check

1. If PCM is found to be faulty during self-diagnostics testing, perform following steps to confirm diagnosis. Most components are incorrectly diagnosed due to faulty electrical connectors or poor connections between component and vehicle. Sometimes, simply disconnecting and connecting a component connector will provide a good electrical connection.
2. Inspect PCM 60-pin harness connector, harness and PCM contact pins for corrosion, bent pins, missing pins, spread terminals and broken wires. Clean, repair or replace as necessary. Check all components, harness and connectors in suspected circuit.
3. Connect PCM 60-pin harness connector to PCM, and retest system using Diagnostic Readout Box (DRB) or similar scan tool. See «TESTS W/CODES - 3.9L»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes-39l) article in the ENGINE PERFORMANCE section. If vehicle does not pass test and fails with same message, replace PCM.

CAMSHAFT POSITION (CMP) SENSOR

Note. In the following test, an analog type voltmeter must be used. Use a small piece of wire (paper clip) to access distributor connector terminals while connector is plugged in.

1. CMP sensor (also known as Hall Effect switch) is located in distributor. Using a ANALOG voltmeter, connect positive voltmeter lead to Tan/Yellow wire at distributor connector. Connect voltmeter negative lead to Black/Light Blue wire at distributor connector.
2. Crank engine. If voltmeter needle fluctuates between zero and 5 volts, CMP sensor functioning properly. If voltmeter reads zero volts, go to next step.
3. Unplug distributor connector. With ignition on, measure voltage between Black/Light Blue wire and Red wire at distributor connector. If voltmeter indicates about 7 volts, replace CMP sensor. If voltmeter reads zero volts, go to next step.
4. Check continuity of Red wire between PCM and distributor connector and Black/Light Blue Wire between distributor harness connector and chassis ground. Repair as necessary. If both wires are okay, Check PCM power and ground circuits. If PCM power and ground circuits are okay, replace PCM.

CRANKSHAFT POSITION (CKP) SENSOR

1. CKP sensor is located in transmission bellhousing near flywheel.
2. Disconnect CKP sensor connector from main wiring harness. Measure resistance across CKP sensor wiring connector terminals "B" and "C". (Scheme 149) Replace CKP sensor if any resistance exists.

Scheme 149

INTAKE MANIFOLD AIR TEMPERATURE SENSOR

1. Intake manifold air temperature sensor is mounted in intake manifold extending into air stream. Sensor is located at right front of manifold under throttle cable bracket.
2. Turn ignition off, disconnect intake manifold air temperature connector. Using DVOM, measure resistance between sensor terminals. See SENSOR RESISTANCE table. If resistance is not within specification, replace intake manifold air temperature sensor.

COOLANT TEMPERATURE SENSOR (CTS)

1. Sensor is located between generator and A/C compressor.
2. With key off, disconnect wire connector from sensor. Connect ohmmeter between sensor terminals. See SENSOR RESISTANCE table. If ohmmeter readings are not within specification, replace CTS.

SENSOR RESISTANCE

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

1. MAP sensor is connected to side of throttle body by a rubber fitting. Inspect rubber connection to sensor, and repair as needed. NOTE: MAP sensor test must be performed with wiring connector connected.
2. Measure MAP sensor output voltage at connector center terminal. With ignition switch in ON position (KOEO), output voltage should be 4.0-5.0 volts. With engine running, sensor output voltage should be 1.5-2.1 volts. Replace MAP sensor if voltage is not as specified.

HEATED OXYGEN SENSOR (HO2S)

To test heating element, measure resistance between the 2 White wire terminals on sensor. Ohmmeter reading should be 5-7 ohms. If ohmmeter does not indicate 5-7 ohms, replace HO2S. To test sensing circuit, see TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

PARK/NEUTRAL POSITION SWITCH

1. Park/neutral position switch is located on transmission. Turn ignition off. Put shift selector in Park position. Disconnect switch harness connector. Using ohmmeter, check continuity between switch center terminal and transmission case. Continuity should exist in Park and Neutral positions only.
2. If continuity exists, switch is functioning properly. If continuity does not exist, check for correct adjustment. Replace switch if correctly adjusted.

Pickup (Some Models With A/T)

Sensor is located next to transmission, in cooler line. With key off, unplug sensor. Connect ohmmeter between sensor terminals. See SENSOR RESISTANCE table. If sensor is suspect, remove sensor and test in heated water with thermometer. Replace sensor if necessary.

THROTTLE POSITION (TP) SENSOR

1. TP sensor is located on throttle body. Disconnect and inspect TP sensor connector. Repair as necessary. With ignition switch in the ON position, measure output voltage at center terminal (output) wire of connector.
2. TP sensor output should read more than 200 millivolts (0.2 volt) at idle. At Wide Open Throttle (WOT), TP sensor output must read less than 4.8 volts.
3. Output voltage should increase gradually as throttle is increased from idle to WOT. If voltage readings are not within specification, replace TP sensor.

Vehicle Speed Sensor (VSS)

VSS is located on transmission extension housing on 2WD models. VSS is located on transfer case on 4WD models. For VSS testing, see TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

AUTO SHUTDOWN (ASD) RELAY

1. ASD relay is located in engine compartment. Relay terminal numbers are stamped on bottom of relay. Relay must be disconnected for testing. If any of the following resistance and continuity tests fail, replace relay.
2. Using an ohmmeter, measure resistance between terminals No. 85 and 86. Resistance should be 70-80 ohms.
3. Connect ohmmeter between terminals No. 87A and 30. Continuity should exist. Connect ohmmeter between terminals No. 87 and 30. Continuity should not exist.
4. Using a pair of jumper wires, connect a jumper wire between terminal No. 85 and battery ground. Connect other jumper wire to battery positive terminal, but DO NOT connect to relay yet. CAUTION: DO NOT allow ohmmeter to contact terminal No. 85 or 86 during following test. Damage to ohmmeter may result.
5. Attach other jumper wire to relay terminal No. 86 to activate relay. Continuity should exist between terminals No. 87 and 30, but not between terminals No. 87A and 30. Disconnect jumper wires from battery and relay.

FUEL DELIVERY

Note. For fuel system pressure testing, see BASIC TESTING - 3.9L article in the ENGINE PERFORMANCE section.

Fuel Injector

Disconnect fuel injector connector. Using a DVOM in ohmmeter mode, measure resistance between pins of injector. If resistance is not 13.3-15.7 ohms, replace fuel injector.

IDLE AIR CONTROL (IAC) MOTOR

See TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - 3.9L article in the ENGINE PERFORMANCE section.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. To locate emission components, refer to emission control information label in engine compartment.

No Air Supply

1. Start engine, and raise engine speed to 1500 RPM. Check air supply at rubber hoses. If air supply increases with RPM, air pump operation is okay. If air pump is okay, check for leakage at hoses and fittings. Repair or replace as necessary.
2. If hoses are okay, check pressure relief valve for leakage. If air is expelled through pressure relief valve at idle, remove air injection check valves.
3. Blow air through check valve in normal direction of air. Air should pass freely. Blow air through opposite direction. Air should not pass. Check exhaust system backpressure. See «BASIC TESTING - 3.9L»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/testing-diagnostics/#engine-controls-basic-testing-39l) article in the ENGINE PERFORMANCE section. If backpressure is okay, replace relief valve.

EXHAUST GAS RECIRCULATION (EGR)

Note. To ensure proper EGR system operation, all passages and moving parts must be free from restrictive deposits. Clean or replace components as necessary.

EGR System Operation Check

1. Warm engine to operating temperature. Check condition of all EGR system tubes, hoses and electrical connections.
2. Start engine. Snap throttle to 2000-2800 RPM and check for EGR valve stem movement. If EGR stem moves, proceed to EGR GAS FLOW TEST. If no stem movement occurs, see «TESTS W/CODES - 3.9L»(/dodge/ram-van-b1500/b-pre-1995-1995/remont/testing-diagnostics/#engine-controls-tests-wcodes-39l) article in the ENGINE PERFORMANCE section for further testing procedures.

EGR Gas Flow Test

1. Warm engine to operating temperature. Disconnect vacuum hose from diaphragm (upper nipple) on EGR valve and attach a hand-held vacuum pump. With engine running, apply 3-5 in Hg. to EGR valve. EGR valve stem should move, and engine should stumble or even stall.
2. If EGR valve stem moved but idle speed remained steady, EGR valve, EGR tube, intake manifold or exhaust manifold may be plugged with carbon. Remove and clean/replace necessary components.
3. If EGR valve stem did not move, reapply vacuum to diaphragm and observe vacuum gauge on vacuum pump. If vacuum leaks down, diaphragm is ruptured and EGR valve must be replaced. If vacuum holds and stem does not move, carefully attempt to clean valve. If cleaning does not free stem, replace EGR valve.

Note. DO NOT use drills or wires to clean passages for EGR control system. Calibration of precision orifices could be altered, resulting in unsatisfactory vehicle operation.

EVAP Canister

EVAP canister is located in engine compartment. Canister has no moving parts. Check for loose, missing, cracked or broken connections and parts. Repair or replace as necessary. No liquid should be in canister.

PCV Valve

1. With engine running at curb idle, remove PCV valve from grommet. If valve is functioning properly, a hissing sound will be heard as air passes through valve.
2. With engine running, place finger over valve inlet. Strong vacuum should be felt at valve inlet. Stop engine. Remove and shake PCV valve to ensure a metallic clicking noise can be heard, indicating valve is free. Reinstall PCV valve.
3. Remove crankcase ventilation filter or oil filler cap from valve cover. Hold a piece of stiff paper over opening. After allowing about one minute for crankcase pressure stabilization, paper should be drawn against opening.
4. If paper is held against opening, performance is okay. If paper is not held against opening, replace PCV valve and retest. If performance does not improve, inspect system for restrictions and clean as necessary.

MISCELLANEOUS CONTROLS

Note. Although some controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

A/C Clutch Relay

See TESTS W/CODES - 3.9L article in the ENGINE PERFORMANCE section.

See also:
• TESTS W/CODES - 3.9L
• BASIC TESTING - 3.9L