Engine Controls - Tests W/codes - 2.6L: Other Isuzu Rodeo I

HARD FAILURES

Hard failures cause CHECK ENGINE light to glow and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. See CODE CHARTS. If a sensor fails, Electronic Control Module (ECM) will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, vehicle runs but driveability will not be optimum.

INTERMITTENT FAILURES

Intermittent failures may cause CHECK ENGINE light to flicker or glow and go out after intermittent fault goes away. However, corresponding trouble code will be retained in Electronic Control Module (ECM) memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from ECM memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.

RETRIEVING CODES

Note. Codes can also be retrieved using a scan tester. Trouble codes may also referred to as DTC. Diagnostic connector may also be referred to as ALDL diagnostic lead or DLC.

1. Code retrieval starts with diagnostic circuit check. See DIAGNOSTIC CIRCUIT CHECK chart under CODE CHARTS. CHECK ENGINE light will come on when ignition is on and engine is not running. When engine is started, CHECK ENGINE light should go off. If light remains on while engine is running, a trouble code is present.
2. If light does not come on with ignition on and engine off, inspect CHECK ENGINE light circuit before continuing. If CHECK ENGINE light fails to operate, see DIAGNOSTIC CIRCUIT CHECK chart.
3. To retrieve codes, install jumper wire between ALDL diagnostic leads. (Scheme 37) Turn ignition on. Count number of flashes from CHECK ENGINE light to identify code. (Scheme 38) For example, Code 12 will be flashed as follows: flash, pause, flash, flash.
4. If system is operating properly, Code 12 should be displayed with ignition on and engine off, indicating diagnostic system is capable of storing codes. Code 12 should be flashed 3 times, followed by any stored trouble codes. Each code will be flashed 3 times starting with lowest code. Once all codes are displayed, cycle will repeat. See «TROUBLE CODE DEFINITION»(ref-16822-S37304245402000122900000). After codes are retrieved, remove jumper wire from diagnostic leads to exit diagnostic mode.

Scheme 37

Scheme 38

CLEARING CODES

1. After repairs are performed, clear ECM memory of all stored codes. Ensure ignition is off. To clear codes, remove fuse No. 3 from instrument panel fuse block, or remove 60-amp MAIN fuse located in engine compartment fuse block.
2. Trouble codes can also be cleared by disconnecting negative battery cable. However, other memory functions (clock, radio, etc.) will need to be reset.

CODE CHARTS

Note. To identify ECM connector terminals, see ECM TERMINAL IDENTIFICATION chart. To test ECM power supply, go to TEST NO. 1 chart.

Circuit Confirmation

1. Disconnect ECM harness connectors.
2. Turn ignition switch to ON position.
3. Ensure battery voltage is present at terminals No. 1, 14 and 4.
4. Ensure continuity exists between terminals No. 11 and 22.

CODE 12 - SYSTEM NORMAL

This DTC No. 12 is always displayed with the key "ON" and the engine not running and it only means that the engine is not running. This DTC No. 12 is not stored in memory.

Note. If the signal DTC No. 12 only is displayed when the function key is operated after clearing the memory, it indicates that the ECM electrical circuits and self-diagnosis system are functioning properly.

CODE 13 - HEATED O2 SENSOR CIRCUIT

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks AIR system operation: Idle engine at normal operating temperature. Stop engine. Disconnect AIR hose at check valve and plug check valve. Restart engine and idle, immediately check direction of airflow.
2. This step tests continuity of oxygen sensor circuit (Red wire) between ECM 22-pin connector terminal No. 20 and oxygen sensor.

Code 13 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 39

CODE 14 - SHORTED ENGINE COOLANT TEMPERATURE SENSOR

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for ECM terminal and connector identification.

ECT Sensor Side Of Black 16-Pin Connector Courtesy Isuzu Motor Co. Scheme 40

Code 14 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 41

CODE 15 - OPEN ENGINE COOLANT TEMPERATURE SENSOR

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for ECM terminal and connector identification.

Code 15 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 42

CODE 21 - THROTTLE VALVE SWITCH (IDLE & FULL THROTTLE)

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for ECM terminal and connector identification.

Code 21 - Throttle Valve Switch Courtesy Isuzu Motor Co. Scheme 43

Code 21 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 44

Code 21 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 45

WOT SWITCH CONTINUITY

CODE 22 - STARTER SIGNAL

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Code 22 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 46

CODE 23, 35, 54 - POWER TRANSISTOR CIRCUIT

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks continuity of power transistor power circuit. Check continuity of ground at ECM terminal No. 13.
2. Inspecting power transistor: Disconnect coil wire at distributor. Attach Spark Tester (J-125) or equivalent to free end of coil wire. Remove power transistor from bottom of intake manifold, and disconnect harness connector. Connect a 2-wire jumper lead between power transistor connector and power transistor. In one wire of jumper lead install a 1.5-volt dry cell battery with negative side of battery facing power transistor. Ground power transistor to frame and turn ignition on. Disconnect and reconnect jumper lead at power transistor connector. Verify spark exists at spark tester. If spark is not present, replace power transistor.

Code 23, 35, 54 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 47

CODE 25, 53 - FUEL PRESSURE REGULATOR VSV

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Test resistance between Light Green/Black wire and Light Green/Yellow wire at VSV connector.

Code 25, 53 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 48

Code 25, 53 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 49

CODE 26, 27 - CANISTER PURGE VSV

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Test resistance between Light Green/Black wire and Green/White wire at VSV connector.

Code 26, 27 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 50

Code 26, 27 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 51

CODE 32 - EGR SYSTEM MALFUNCTION

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Specified Reappearance Pattern: Run engine at idle and normal operating temperature. Keep vehicle at idle for more than 10 minutes at stop. Drive vehicle at 10 MPH. Accelerate to more than 30 MPH. After 10-30 seconds, decelerate to complete stop. Repeat pattern several times.
2. This step checks EGR operation by re-applying signal vacuum.

Scheme 52

Code 32 - Diagnostic Flowchart (1 Of 3) Courtesy Isuzu Motor Co. Scheme 53

Code 32 - Diagnostic Flowchart (2 Of 3) Courtesy Isuzu Motor Co. Scheme 54

Code 32 - Diagnostic Flowchart (3 Of 3) Courtesy Isuzu Motor Co. Scheme 55

CODE 33 - FUEL INJECTOR CIRCUIT (OPEN OR GROUNDED)

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Code 33 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 56

CODE 34 - EGR GAS TEMPERATURE SENSOR

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Code 34 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 57

Code 34 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 58

CODE 41 - CRANK ANGLE SENSOR SIGNAL

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Inspecting Crankshaft Position (CKP) sensor circuit: Disconnect CKP sensor and ECM connectors. Turn ignition on. Measure CKP sensor voltage and resistance values. See CKP SENSOR SPECIFICATIONS table. If values are not within specification, repair or replace appropriate harness or connector. Reconnect CKP and ECM connectors.

CKP SENSOR SPECIFICATIONS

Scheme 59

CODE 43, 65 - THROTTLE VALVE SWITCH

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for ECM terminal and connector identification.

Code 43, 65 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 60

WOT SWITCH CONTINUITY

CODE 44, 45 - OXYGEN SENSOR-LEAN/RICH FUEL MIXTURE

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Measure voltage at oxygen sensor connector.
2. Jumper wire allows voltage measurement of circuit.

Code 44, 45 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 61

Code 44, 45 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 62

CODE 51, 52 - FAULTY ECM RAM/ROM

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Note. Test numbers refer to numbers on diagnostic chart.

1. Before replacing ECM, check circuit connections: Disconnect ECM harness connectors. Inspect all terminals and repair as necessary. Reconnect ECM harness connectors, and road test vehicle. Check for codes. If condition persists or code reappears, replace ECM.

Code 51, 52 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 63

CODE 61, 62 - AIRFLOW SENSOR SIGNAL

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Code 61, 62 - Diagnostic Flowchart (1 Of 2) Courtesy Isuzu Motor Co. Scheme 64

Code 61, 62 - Diagnostic Flowchart (2 Of 2) Courtesy Isuzu Motor Co. Scheme 65

CODE 63 - VEHICLE SPEED SENSOR SIGNAL

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for terminal and connector identification.

Code 63 can be set, without a system failure, under following conditions

1. Auto. Trans. In Drive position, with brake pedal depressed and accelerator pedal depressed more than halfway for more than 3 seconds.
2. Manual Trans. Under severe climbing conditions, with vehicle stationary, accelerator pedal depressed more than halfway for more than 3 seconds, and clutch partially engaged.

Note. Test numbers refer to numbers on diagnostic chart.

1. Check for continuity between ECM 22-pin connector terminal No. 5 (White/Green wire) and ground. Disconnect speedometer cable at transmission. Tester should pulsate between open and continuity as speedometer cable is rotated slowly. NOTE: Instrument cluster has two 12-pin connectors. Ensure appropriate wire color is tested.
2. Ensure continuity exists on White/Green wire between ECM 22-pin connector terminal No. 5 and instrument cluster 12-pin connector terminal No. 9. Ensure continuity exists on Black/White wire between instrument cluster 12-pin connector terminal No. 9 and ground.
3. Remove instrument cluster assembly. Check continuity between terminals No. 1 and 2. Tester should pulsate between open and continuity as speedometer inner shaft is rotated slowly.

Instrument Cluster Connections Courtesy Isuzu Motor Co. Scheme 66

Code 63 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 67

CODE 64 - FUEL INJECTOR CIRCUIT (ECM TRANSISTOR)

Note. See appropriate wiring diagram in WIRING DIAGRAMS article for ECM terminal and circuit identification.

Code 64 - Diagnostic Flowchart Courtesy Isuzu Motor Co. Scheme 68

SUMMARY

If no hard fault codes (or only pass codes) are present, driveability symptoms exist or intermittent codes exist, proceed to TROUBLE SHOOTING - NO CODES - FUEL INJECTION article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.