Engine Controls - System & Component Testing: Other Isuzu Axiom I

POWERTRAIN CONTROL MODULE

Note. For PCM pin and terminal identification, see PIN VOLTAGE CHARTS or WIRING DIAGRAMS articles.

Note. To perform the following ground and power tests, see WIRING DIAGRAMS article.

Ground Circuits

1. Turn ignition off. Disconnect specified PCM harness connectors. Using a DVOM, measure resistance between ground and PCM ground terminals. See «POWERTRAIN CONTROL MODULE GROUND CIRCUIT TERMINALS»(ref-133140-S07481277072002021300000) table. Resistance should be zero ohms. If problem is found, locate and repair open suspect circuit. If no problem is found, go to next step. POWERTRAIN CONTROL MODULE GROUND CIRCUIT TERMINALS Vehicle & PCM Harness Connector Terminal No. Axiom (1) E-34 (Blue) 1 & 40 E-35 (Red) 1, 23 & 40 Passport (1) F (Blue) F1 & F40 S (Red) S1, S23 & S40 Rodeo (2.2L) & Rodeo Sport (2.2L) (2) C-2 (White) C8 & C9 Rodeo (3.2L), Rodeo Sport (3.2L) & Trooper (1) E-21 (Blue) 1 & 40 E-22 (Red) 1, 23 & 40 (1) On Axiom, Passport, Rodeo and Rodeo Sport 3.2L, PCM is located at left rear of engine compartment, near air filter housing. On Trooper, PCM is located at right rear of engine compartment. (2) On Rodeo and Rodeo Sport 2.2L, PCM is located under center console in front of shifter. To access PCM, see «POWERTRAIN CONTROL MODULE REPLACEMENT»(ref-133138-S03776365552002081900000) under POWERTRAIN CONTROL MODULE in SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L article.
2. Reconnect PCM harness connectors. Using a DVOM, connect negative lead to ground and backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is more than specified, check ground circuit for open, short, corrosion or loose connection. If problem is found, repair as necessary.

Power Circuits

Using DVOM, backprobing measure voltage between ground and appropriate PCM harness connector terminals. See POWERTRAIN CONTROL MODULE POWER CIRCUIT TERMINALS table. If battery voltage is not present, check ignition related fuses. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If circuits test okay, check for a defective ignition switch.

POWERTRAIN CONTROL MODULE POWER CIRCUIT TERMINALS

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For pin and terminal identification, see WIRING DIAGRAMS or PIN VOLTAGE CHARTS articles.

Exhaust Gas Recirculation System Check

1. Check EGR valve for looseness. If EGR valve is loose, tighten fasteners as necessary. If no problem is found, go to next step.
2. Start engine, and run until engine is at normal operating temperature. Connect Tech 2 or equivalent scan tool to Data Link Connector (DLC). DLC is located under small cover on lower left side of instrument panel. On scan tool, select MISCELLANEOUS TESTS and then EGR TEST. Using scan tool, command EGR valve 50 percent On. If engine begins to run roughly and loses RPM, testing is complete. If engine does not perform as specified, go to next step.
3. Turn ignition off. Disconnect EGR valve 5-pin harness connector. Using test light connected to ground, probe EGR valve ignition feed circuit. See «IDENTIFYING EGR VALVE IGNITION CIRCUITS»(ref-133140-S38050823382002092000000) table. If test light illuminates, go to step 5 . If test light does not illuminate, go to next step. IDENTIFYING EGR VALVE IGNITION CIRCUITS Model Terminal No. (Wire Color) Except Trooper 4 (Gray/Red) Trooper 4 (Red/Blue)
4. Repair open or short to ground in EGR valve ignition feed circuit between PCM and EGR valve. See «WIRING DIAGRAMS»(ref-133147) article. After repair, repeat step 2 .
5. Remove EGR valve. Check EGR pintle, valve passages and adapter for excessive deposits, obstructions or restrictions. If problem is found, go to next step. If no problem is found, go to step 7 .
6. Clean or replace EGR valve or components as necessary. After repair, go to next step.
7. Holding EGR valve case to ground. Using scan tool, command EGR ON. Observe EGR valve pintle for movement. If EGR pintle moves as commanded, go to next step. If EGR pintle does not move as commanded, perform DTC P1406 in «SELF-DIAGNOSTICS - TROOPER 3.5L»(ref-133137) or «SELF-DIAGNOSTICS - AXIOM 3.5L, PASSPORT, RODEO & RODEO SPORT 3.2L»(ref-142539) article. For Rodeo and Rodeo Sport 2.2L, perform DTC P0404 in «SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L»(ref-133138) .
8. Remove EGR inlet and outlet pipes from intake and exhaust manifolds. Check for excessive deposits, obstructions or restrictions. If problem is found, clean or replace EGR valve or components as necessary. After repair, repeat step 2 .

Common Components

1. Fuel tank.
2. EVAP vent solenoid.
3. Fuel Vapor Pressure (FVP) sensor.
4. Fuel pipes & hoses.
5. Vapor lines.
6. Fuel cap.
7. EVAP canister.
8. Purge lines.
9. EVAP canister cut valve (purge solenoid).

Required Service

The Positive Crankcase Ventilation (PCV) system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or slow idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles roughly, check for clogged PCV valve and for plugged or broken PCV hoses BEFORE adjusting idle. Check for correct PCV valve application to ensure the correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Remove PCV valve from rocker cover grommet. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in intake manifold port, hoses or PCV valve. If problem is found, repair or replace as necessary.
2. Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside PCV valve. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits that may make PCV valve sticky, restricted or incompletely seated. If problem is found, replace if necessary.
4. Engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. Since an engine operating without any crankcase ventilation can be damaged, it is important to replace PCV valve and air cleaner breather at regular intervals. Check all hoses and clamps for failure or deterioration. If problem is found, repair or replace as necessary.

ENGINE COOLANT TEMPERATURE SENSOR

To test Engine Coolant Temperature (ECT) sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

HEATED OXYGEN SENSOR

To test Heated Oxygen Sensor (HO2S) related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

INTAKE AIR TEMPERATURE SENSOR

To test Intake Air Temperature (IAT) sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

MANIFOLD ABSOLUTE PRESSURE SENSOR

To test Manifold Absolute Pressure (MAP) sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

MASS AIR FLOW SENSOR

To test Mass Air Flow (MAF) sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

THROTTLE POSITION SENSOR

To test Throttle Position (TP) sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

TRANSMISSION TEMPERATURE SENSOR

Note. Transmission temperature sensor may also be referred to as Transmission Fluid Temperature (TFT) sensor.

For diagnosis and testing information, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

TRANSMISSION RANGE SWITCH

To test Transmission Range (TR) switch related problem, see appropriate SELF-DIAGNOSTICS article. For additional information, appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

VEHICLE SPEED SENSOR

To test Vehicle Speed Sensor (VSS) related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

FUEL SYSTEM

ELECTRONIC THROTTLE CONTROL SYSTEM

See ELECTRONIC THROTTLE CONTROL SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article.

FUEL DELIVERY

Note. For fuel system delivery testing, see FUEL PUMP FLOW TEST procedure in BASIC DIAGNOSTIC PROCEDURES article.

FUEL PRESSURE REGULATOR

For fuel pressure regulator testing, see appropriate FUEL SYSTEM DIAGNOSIS procedure in BASIC DIAGNOSTIC PROCEDURES article.

Fuel Injector(s)

Disconnect fuel injector 2-pin harness connector. Measure resistance across injector terminals. Resistance should be as specified. See FUEL INJECTOR COIL RESISTANCE table.

FUEL INJECTOR COIL RESISTANCE

FUEL SYSTEM PRESSURE RELEASE

Loosen fuel tank filler cap to relieve tank pressure. Remove fuel pump relay from underhood fuse/relay box. Start and operate engine until it stalls. Crank engine an additional 3 seconds.

FUEL TANK LEAK CHECK

1. Relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-133140-S00335660722002091900000) . Remove fuel tank. See FUEL TANK under «FUEL SYSTEM»(ref-133146-S21790669332002021300000) in REMOVAL, OVERHAUL & INSTALLATION article. Plug filler neck, vent hoses and fuel lines.
2. Install short piece of fuel line on fuel tank meter vent tube. Apply approximately 1-1.5 psi (7-10 kPa) of air pressure to tank through vent tube. Test suspect area with soap solution or by submersion. If leak is found, replace tank.

IDLE AIR CONTROL SYSTEM CHECK (RODEO & RODEO SPORT 2.2L)

Note. IAC motor analyzer (J39027-A) is required to test IAC valve.

Note. For pin and terminal identification, see WIRING DIAGRAMS or PIN VOLTAGE CHARTS articles.

IDLE AIR CONTROL VALVE (AXIOM & TROOPER)

To test idle control system, see appropriate DTC under DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

IGNITION SYSTEMS

If engine cranks but does not run or immediately stalls, perform appropriate ENGINE CRANKS BUT WILL NOT RUNtesting procedure under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article. Engine cranks but will not run diagnostic procedure will determine if problem is in the ignition or fuel systems. If any DTC are stored, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article. If misfire is being experienced and no DTCs are stored, see MISFIRE MONITOR DIAGNOSIS .

CAMSHAFT POSITION SENSOR

To test Camshaft Position Sensor (CMP) related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

CRANKSHAFT POSITION SENSOR

To test Crankshaft Position Sensor (CKP) related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

IGNITION COILS

To test ignition coil or cylinder misfire related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

ION SENSING MODULE

To test ION sensing module related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

KNOCK SENSOR

To test knock sensor related problem, see related DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

TIMING CONTROL SYSTEMS

To test timing control, see appropriate DTC under DIAGNOSTIC TROUBLE CODE DEFINITIONS in appropriate SELF-DIAGNOSTICS article.

A/C CLUTCH CONTROL (RODEO & RODEO SPORT 2.2L)

For A/C clutch control testing see, DTC P1546: A/C COMPRESSOR CLUTCH OUTPUT CIRCUIT in SELF-DIAGNOSTICS - RODEO & RODEO SPORT 2.2L article.

A/C CLUTCH RELAY

1. Disconnect A/C clutch relay. A/C clutch relay is located in under-hood fuse/relay box. Using proper mini-schematic and DVOM, check continuity between A/C clutch relay winding terminals. See WIRING DIAGRAMS in appropriate A/C-HEATER SYSTEMSarticle. Continuity should be present. Check continuity between clutch drive circuit terminals of relay. Continuity should not be present.
2. Using jumper wires, apply ground and battery voltage to relay winding terminals. Continuity should now be present between clutch drive circuit terminals of relay. Replace A/C clutch relay if continuity is not present.

BRAKE LIGHT SWITCH (RODEO & RODEO SPORT 2.2L)

1. Disconnect brake light switch 2-pin harness connector. Using an ohmmeter, check continuity between brake light switch terminals No. 1 and 4. For terminal identification, see «WIRING DIAGRAMS»(ref-133147) article. Continuity should not be present. Depress brake pedal or actuate brake light switch, continuity should be present. Replace switch if continuity is not as specified.
2. Check for battery voltage at brake light switch harness connector. If battery voltage is not present, check CB-6 STOP LIGHT (15-amp) fuse in dash fuse box. If fuse is okay, check battery feed wire for an open or short. If problem is found, repair as necessary. After repair, verify brake light operation.

BRAKE LIGHT SWITCH (AXIOM, PASSPORT, RODEO 3.2L & RODEO SPORT 3.2L)

For testing procedure, see DTC P0571: NO BRAKE SWITCH SIGNAL in SELF-DIAGNOSTICS - AXIOM 3.5L, PASSPORT, RODEO 3.2L & RODEO SPORT 3.2L article.

BRAKE LIGHT SWITCH (TROOPER)

For testing procedure, see DTC P1574: BRAKE SWITCH NO OPERATION in SELF-DIAGNOSTICS - TROOPER article.

BRAKE LIGHT SWITCH WITH CRUISE CONTROL

Test brake light circuit. See appropriate BRAKE LIGHT SWITCH procedure. Using an ohmmeter, check for continuity between terminals No. 2 and 3. Continuity should be present. Depress brake pedal, to deactivate cruise control. Continuity should not be present. Replace switch if not as specified.

MALFUNCTION INDICATOR LIGHT DOES NOT ILLUMINATE OR REMAINS ILLUMINATED

See testing procedure in appropriate SELF-DIAGNOSTICS article.

MISFIRE COUNTERS

Whenever a cylinder misfires, misfire diagnostic counts misfires and notes crankshaft position at the time misfire occurred. These "misfire counters" are basically a file on each cylinder. A current and history misfire counter are maintained for each cylinder. Current misfire counters (MISFIRE CUR #1-6) indicate number of firing events out of the last 100 cylinder firing events which were misfires. Current misfire counter will display real time data without a misfire DTC stored. History misfire counters (MISFIRE HIST #1-6) indicate total number of cylinder firing events which were misfires. History misfire counters will display "0" until misfire diagnostic has failed and a DTC P0300 is set. Once misfire DTC P0300 is set, history misfire counters will be updated every 100 cylinder firing events. A misfire counter is maintained for each cylinder. If misfire diagnostic reports a failure, diagnostic executive reviews all misfire counters before reporting DTC. This way diagnostic executive reports most current information. When crankshaft rotation is erratic, a misfire condition will be detected. Because of this erratic condition, data that is collected by the diagnostic can sometimes incorrectly identify which cylinder is misfiring. Misfires are counted for more than one cylinder. If cylinder No. 1 has the majority of counted misfires. In this case, Misfire counters would identify cylinder No. 1 as misfiring cylinder. Misfires in the other counters were just background noise caused by erratic misfire rotation of the crankshaft. If the number of accumulated misfires is sufficient for the diagnostic to identify a true misfire, the diagnostic will set DTC P0300. Use diagnostic equipment to monitor misfire counter data on OBD II-compliant vehicles. Knowing which specific cylinder(s) misfired can lead to root cause, even when dealing with a multiple cylinder misfire. Using information in misfire counters identifies which cylinders are misfiring. If misfire counter indicates cylinders 1 and 4 misfired, look for a circuit or component common to both cylinders. On scan tool, misfire counter information is located in the "Eng". menu, "Misfire Data" sub-menu of the data list. Misfire diagnostic may indicate a fault due to a temporary fault not necessarily caused by a vehicle emission system malfunction. Examples include following items

1. Contaminated fuel.
2. Low fuel.
3. Fuel-fouled spark plugs.
4. Basic engine fault.

Ignition Control Module

See appropriate ENGINE CRANKS BUT WILL NOT RUN under NO START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.

For PCM diagnosis, see POWERTRAIN CONTROL MODULE in appropriate SELF-DIAGNOSTICS article.

Main Relay

Note. Main relay can also be referred to as PCM or ECM relay.

This 4-terminal relay is located in underhood fuse/relay box. Main relay is used for PCM power control. For terminal identification, see appropriate wiring diagram in WIRING DIAGRAMS article.

Fuel Pump Relay

This 4 or 5-terminal relay is located in underhood fuse/relay box. Fuel pump relay is used to power in-tank fuel pump. When ignition is turned to ON position, fuel pump relay sends signal to in-tank fuel pump for 2 seconds. When engine is started PCM receives signal from ignition control module (Passport, Rodeo and Rodeo Sport) or 58X reference signal (Axiom and Trooper). PCM signals fuel pump relay to operate in-tank fuel pump. For terminal identification, see appropriate wiring diagram in WIRING DIAGRAMS article. For testing procedure, see RELAY TESTunder MISCELLANEOUS TESTin appropriate SELF-DIAGNOSTICS article.

A/C Compressor Clutch

A/C Compressor Clutch relay is located in underhood fuse/relay box. A 12-volt signal is supplied to A/C request input of PCM when A/C is selected through the A/C control switch. A/C compressor clutch relay is controlled through PCM. This allows PCM to modify idle air control position prior to A/C clutch engagement for better idle quality. If engine operating conditions are within their specified calibrated acceptable ranges, PCM will enable the A/C compressor relay. This is done by providing a ground path for the A/C relay coil within the PCM. When A/C compressor relay is enabled, battery voltage is supplied to A/C compressor clutch coil. PCM will enable A/C compressor clutch whenever engine is running and A/C has been requested. PCM will not enable A/C compressor clutch if any of the following conditions are met

1. Engine speed is 6315 RPM or more.
2. ECT is 246°F (119 °C) or more.
3. Throttle is more than 80% open.