Engine Controls - System/component Tests - 5.2l Jeep Grand Cherokee ZJ

INTRODUCTION

Note. Testing procedures not covered in this article require a Chrysler Diagnostic Readout Box (DRB). See appropriate TESTS W/CODES - 5.2L article in this section.

Before testing individual components or systems, perform procedures in BASIC TESTING - 5.2L article in this section. Since many computer controlled and monitored components set a fault message if they malfunction, also perform procedures in TESTS W/CODES - 5.2L article in this 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 - 5.2L»(/jeep/grand-cherokee/zj-1992-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes-52l) article in this section. If vehicle does not pass test and fails with same message, replace PCM.

INTAKE MANIFOLD AIR TEMPERATURE SENSOR

Intake manifold air temperature sensor is mounted in intake manifold extending into air stream. On 5.2L engine, sensor is located at right front of manifold behind alternator. Turn ignition off, disconnect intake manifold air temperature connector. Using DVOM, measure resistance between sensor terminals. See SENSOR RESISTANCE . If resistance is not within specification, replace intake manifold air temperature sensor.

COOLANT TEMPERATURE SENSOR (CTS)

1. On 5.2L models, sensor is located between alternator and A/C compressor.
2. With key off, disconnect wire connector from sensor. Connect ohmmeter between sensor terminals. See «SENSOR RESISTANCE»(/jeep/grand-cherokee/zj-1992-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-52l) table. If ohmmeter readings are not within specification, replace CTS.

SENSOR RESISTANCE

CRANKSHAFT POSITION (CKP) SENSOR

1. The CKP sensor is bolted to cylinder block near rear of right cylinder head, at bellhousing of transmission.
2. Disconnect CKP sensor connector from main wiring harness. Measure resistance across CKP sensor wiring connector terminals "B" and "C". (Scheme 79) Replace CKP sensor if any resistance exists.

Scheme 79

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

1. On 5.2L models, MAP sensor is connected to side of throttle body by a rubber fitting. Inspect rubber connection to sensor, and repair as needed.
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 ignition switch in RUN position (KOER), voltage should be 1.5-2.1 volts. Replace MAP sensor if it fails testing as specified.

OXYGEN (O2) SENSOR

See TESTS W/CODES - 5.2L article in this 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.
2. If continuity exists, switch is functioning properly. Continuity should also exist in Neutral position. If continuity does not exist, check for correct adjustment. Replace switch if correctly adjusted.

Scheme 80

THROTTLE POSITION SENSOR (TPS)

1. TPS is located on throttle body. Disconnect and inspect TPS connector. Repair as necessary. With ignition switch in the ON position, measure output voltage at center terminal (output) wire of connector.
2. On 5.2L models, TPS output should read more than 200 millivolts at idle. At Wide Open Throttle (WOT), TPS 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 TPS.

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 - 5.2L article in this section.

Idle Air Control (IAC) Motor

See TESTS W/CODES - 5.2L article in this 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 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 appropriate BASIC TESTING - 5.2L article in the ENGINE PERFORMANCE section.

Fuel Injector

On 5.2L, disconnect fuel injector connector. Using a DVOM in ohmmeter position, test between pins of injector for resistance. Resistance should be 13.3-15.7 ohms, replace fuel injector as necessary.

See TESTS W/CODES - 5.2L article in this section.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - 5.2L article in this 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 diverter valve for leakage. If air is expelled through diverter exhaust with vehicle at idle, replace diverter valve. If diverter valve is okay, remove check valve. Blow air through check valve in direction of air pump. Air should not pass through. Blow air through opposite direction. Air should pass freely.

Air Pump

Check and adjust belt tension (if necessary). Disconnect air supply hose from by-pass control valve. Start engine. Pump is operating correctly if airflow is felt at pump outlet and airflow increases as engine speed increases. If pump does not operate as specified, replace pump.

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. Attach a tachometer to engine. Run engine at idle in Neutral an additional 70 seconds.
2. Accelerate engine speed abruptly to 2000-3000 RPM, and check EGR valve stem for movement. Repeat test to confirm stem movement, indicating EGR control system is functioning correctly. If EGR valve stem does not move, connect external vacuum source and recheck EGR valve stem for movement. If EGR operates normally on external vacuum source, go to step 6).
3. If EGR valve stem does not move, check for cracked, leaking, disconnected or plugged vacuum hoses. Verify correct hose routing. Disconnect hose harness from EGR valve/transducer, and connect a vacuum pump to harness.
4. Start engine, and raise engine speed to 2000 RPM and hold. Apply 10 in. Hg vacuum to EGR while checking for EGR valve movement. If no movement occurs, see «TESTS W/CODES - 5.2L»(/jeep/grand-cherokee/zj-1992-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes-52l) article in this section.
5. If valve opens approximately 1/8" (3 mm), hold vacuum constant and check for valve diaphragm leakage. Valve should remain open for at least 30 seconds. If leakage occurs, replace valve/transducer assembly. If valve is okay, check control system.
6. If EGR valve stem does not move in step 2) but operates normally on external vacuum source, remove throttle body and check port in throttle bore for blockage. Use a solvent to remove deposits, and check flow using light air pressure. Normal operation should be restored.
7. If engine will not idle correctly or stalls, check for leaking EGR valve. With engine running, remove vacuum hose from EGR valve. If removing vacuum hose does not correct rough idle, remove EGR valve/transducer assembly. Check valve for proper seating. Replace assembly as necessary.
8. Also check EGR-to-intake manifold tube for leak. Remove tube and inspect gasket. Tube end should be uniformly indented on gasket, without signs of leakage. If leakage is not evident, replace gaskets and tighten flange nuts to 17 ft. lbs. (23 N.m). If leak persists, replace EGR tube and gaskets.

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 - 5.2L article in this section.

See also:
• TESTS W/CODES - 5.2L
• BASIC TESTING - 5.2L
• SENSOR RESISTANCE