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

POWERTRAIN CONTROL MODULE (PCM)

Note. To perform the following ground and power tests, use appropriate wiring diagram in WIRING DIAGRAMS article.

Ground Circuits

1. Disconnect PCM connectors. Using an ohmmeter, check for continuity to ground on PCM harness ground terminals. See «PCM GROUND CIRCUIT TERMINALS»(ref-91054-S28677315482001030100000) table. Resistance should be zero ohms. If not, locate and repair open in wire. PCM GROUND CIRCUIT TERMINALS Vehicle PCM Connector Terminal No. Hombre C1 18 C1 60 C2 21 Except Hombre White C7 White C8 White C9
2. Reconnect PCM connectors. Using a voltmeter, connect negative lead of voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, short, corrosion or loose connection on ground circuit. Repair as necessary.

Power Circuits

Turn ignition on. Using a voltmeter, backprobe PCM harness connectors. Check for battery voltage between PCM ignition power terminals and ground. See PCM BATTERY CIRCUIT TERMINALS table. If battery voltage is not present, check IGN fuse and fusible links. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If okay, check for a defective ignition switch.

PCM POWER CIRCUIT TERMINALS

Engine Coolant Temperature (ECT) Sensor

If a coolant sensor-related code is present, see appropriate SELF-DIAGNOSTICS article.

Oxygen Sensor (O2S)

If an O2S related code is present, see appropriate SELF-DIAGNOSTICS article.

Heated Oxygen Sensor (HO2S)

If an HO2S related code is present, see appropriate SELF-DIAGNOSTICS article.

Intake Air Temperature (IAT) Sensor

If an IAT sensor-related code is present, see appropriate SELF-DIAGNOSTICS article.

Knock Sensor (KS)

If a KS-related code is present, see appropriate SELF-DIAGNOSTICS article.

Manifold Absolute Pressure (MAP) Sensor

If a MAP sensor-related code is present, see appropriate SELF-DIAGNOSTICS article.

Mass Air Flow (MAF) Sensor (Amigo, Passport, Rodeo, SLX, Trooper & VehiCROSS)

If a MAF sensor-related code is present, see appropriate SELF-DIAGNOSTICS article.

Throttle Position (TP) Sensor

If a TP sensor-related code is present, see appropriate SELF-DIAGNOSTICS article.

Transmission Temperature Sensor (SLX, Trooper & VehiCROSS)

Disconnect transmission temperature sensor. Measure resistance across terminals of sensor connector. Replace sensor if resistance is not within specification. See TRANSMISSION TEMPERATURE SENSOR RESISTANCE table.

TRANSMISSION TEMPERATURE SENSOR RESISTANCE

Transmission Range (TR) Switch

If a TR switch-related code is present, see appropriate SELF-DIAGNOSTICS article.

VEHICLE SPEED SENSOR (VSS)

If a VSS code is present, see appropriate SELF-DIAGNOSTICS article.

Ignition Control Module

See ENGINE CRANKS BUT WILL NOT RUN in BASIC DIAGNOSTIC PROCEDURES article.

Idle Air Control

See IDLE CONTROL SYSTEM .

Main Relay (Amigo, Passport, Rodeo, SLX, Trooper & VehiCROSS)

This 4-terminal relay is located in under-hood fuse box. Main relay is used for PCM power control. See WIRING DIAGRAMS article for terminal identification.

FUEL SYSTEM

FUEL DELIVERY

Note. For fuel system pressure testing, see appropriate FUEL SYSTEM DIAGNOSIS 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 Pump Relay

See FUEL SYSTEM ELECTRICAL TEST in BASIC DIAGNOSTIC PROCEDURES article.

Fuel Injector(s)

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

FUEL INJECTOR COIL RESISTANCE

Fuel Injector Coil

See appropriate SELF-DIAGNOSTICS article.

FUEL TANK LEAK CHECK

1. Relieve fuel system pressure. See FUEL SYSTEM PRESSURE RELEASE in REMOVAL, OVERHAUL & INSTALLATION article. Remove fuel tank. 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 (IAC) Valve

See appropriate SELF-DIAGNOSTICS article.

Ignition Control Circuit

See appropriate SELF-DIAGNOSTICS article.

Knock Sensor (KS) Circuit

See appropriate SELF-DIAGNOSTICS article.

Linear EGR Valve

See appropriate SELF-DIAGNOSTICS article.

EGR Valve Check

With engine off, disconnect vacuum hose to EGR valve. Connect vacuum pump to EGR and apply 10 in. Hg. EGR diaphragm should move up and stay up for at least 20 seconds. If not, replace EGR valve.

EVAP Canister Control System

See appropriate SELF-DIAGNOSTICS article.

Required Service

The 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 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. 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 manifold port, hoses or PCV valve. 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. 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.

Brake Light Switch (Amigo, Passport, Rodeo, SLX, Trooper & VehiCROSS)

1. Disconnect brake light switch harness connector. Using an ohmmeter, check continuity between brake light switch terminals No. 1 and 2. See WIRING DIAGRAMS article for terminal identification. Continuity should not be present. Depress brake pedal or activate brake light switch, continuity should be present. Replace switch if not as specified.
2. Check for battery voltage at brake light switch connector. If battery voltage is not present, check 20A STOP-HAZARD fuse in fuse box. If fuse is okay, check battery feed wire for an open or short. Repair as necessary.

Brake Light Switch with Cruise Control (Amigo, Passport, Rodeo, SLX, Trooper & VehiCROSS)

Test brake light circuit. See BRAKE LIGHT SWITCH . Using an ohmmeter, check for continuity between terminals No. 3 and 4. Continuity should exist. Depress brake pedal, to deactivate cruise control. Continuity should not exist. Replace switch if not as specified.

A/C Clutch Relay

1. Disconnect A/C clutch relay harness connector. For A/C clutch relay locations, see «A/C COMPRESSOR CLUTCH RELAY LOCATION»(ref-91054-S19214187242001030100000) table. Using proper mini-schematic and an ohmmeter, check continuity between A/C clutch relay winding terminals. See WIRING DIAGRAMS article. Continuity should exist. Check continuity between clutch drive circuit terminals of relay. Continuity should not exist. A/C COMPRESSOR CLUTCH RELAY LOCATION Application Location Amigo, Passport, Rodeo, SLX , Trooper & VehiCROSS In Under-Hood Fuse/Relay Box Hombre On Bracket, On Left Side Of Firewall
2. Using jumper wires, apply ground and battery voltage to relay winding. Continuity should now exist between clutch drive circuit terminals of relay. Replace A/C clutch relay if continuity does not exist.