SELF-DIAGNOSTIC SYSTEM
Self-diagnostic system is used for diagnosing malfunctions of Electronic Concentrated Control System (ECCS) sensors and actuators. Electronic Control Module (ECM) has 2 available diagnostic modes. Before entering self-diagnostics, perform BASIC DIAGNOSTIC PROCEDURES. This prevents wasted diagnostic time and invalid diagnostic results.
DIAGNOSTIC MODES
Self-diagnostic system can detect ECCS malfunctions and store related trouble codes. Intermittent codes are also stored. All codes are stored until cleared from memory. If an intermittent fault does not reoccur within 50 ignition key cycles, it will be cleared from memory.
Switching modes is not possible when engine is running. During diagnosis, self-diagnostic system will automatically return to Mode I from Mode II when ignition is turned off.
ENTERING SELF-DIAGNOSTICS
- Turn ignition on, but leave engine off. Using a small screwdriver, turn diagnostic mode selector on ECM fully clockwise. Wait at least 2 seconds, and then turn diagnostic mode selector fully counterclockwise. Mode II self-diagnostics will result, and MIL and Red LED inspection light will flash codes (if present).
- If engine is started at this stage, MIL and Red LED inspection light will display condition of air/fuel mixture, monitored by HO2S sensor, whether system is in closed or open loop.
Note. Turn diagnostic mode selector fully counterclockwise whenever vehicle is in use. Switching modes is not possible when engine is running.
TROUBLE CODE DEFINITION
Note. When DTC tests indicate to check a component, see indicated component in I - SYS/COMP TESTS article. For Diagnostic Trouble Code (DTC) illustration symbol identification (Scheme 1) To identify ECM connector terminals, see WIRING DIAGRAMS article.
| Code | System Affected | Probable Cause |
|---|---|---|
| 11 (1) | Camshaft/Crankshaft Position Sensor | (2) No Crank Signal |
| 12 | Mass Airflow Sensor Circuit | Open/Shorted Circuit |
| 13 | Engine Coolant Temperature Sensor | Open/Shorted Circuit |
| 14 | Vehicle Speed Sensor (VSS) | No VSS Signal |
| 21 (1) | Ignition Signal Circuit | (2) Open/Shorted Circuit |
| 31 | ECM | Signals Not Normal |
| 32 (3) | EGR Function | No EGR Operation |
| 33 | HO2S Sensor (LEFT) | Open/Shorted Circuit/High HO2S Signal |
| 34 (1) | Knock Sensor | Open/Shorted Circuit |
| 35 (3) | EGR Temperature Sensor | Open/Shorted Circuit |
| 42 (1) | Fuel Temperature Sensor | Open/Shorted Circuit |
| 43 | Throttle Position Sensor | Open/Shorted Circuit |
| 45 (3) | Injector Leak. | Leak At Injectors |
| 51 (4) | Injector Circuit | Injector Does Not Work. |
| 53 | HO2S Sensor (Right). | Open/Shorted Circuit/High HO2S Signal |
| 54 (1) | Automatic Transmission Signal | Open Signal Transmission Control Unit. |
| 55 (1) | No Malfunction | Normal Condition |
| (1) Trouble code will not activate Malfunction Indicator Light (MIL). (2) If Codes 11 and 21 are present at same time3, check items causing a malfunction of camshaft/rankshaft position sensor circuit first. (3) California models. (4) Models with automatic transmission, Serial No. 450021 and later. | ||
| (1) | Trouble code will not activate Malfunction Indicator Light (MIL). |
| (2) | If Codes 11 and 21 are present at same time3, check items causing a malfunction of camshaft/rankshaft position sensor circuit first. |
| (3) | California models. |
| (4) | Models with automatic transmission, Serial No. 450021 and later. |
TROUBLE CODE IDENTIFICATION
Scheme 1
DIAGNOSTIC TROUBLE CODE (DTC) TESTING (J30)
Note. Procedures using CONSULT Tester (J-38465) will be shown when available. If CONSULT Tester is not available, disregard steps using CONSULT Tester and use alternate test procedure.
Note. In the following DTC testing, when instructed to perform "FINAL CHECK", see FINAL CHECK in this article.
DTC 31: ECM
Turn ignition on. Erase Diagnostic Test Mode II (Self-Diagnostic Results) memory. Perform Diagnostic Test Mode II (Self-Diagnostic Results). If ECM displays DTC 31 again, replace ECM.
3) Perform Diagnostic Test Mode II (Self-Diagnostic Results)
IF DTC does not return, inspection is completed. If DTC 45 displays, relieve fuel pressure and remove injector assembly. See REMOVAL, OVERHAUL & INSTALLATION article. Do not remove fuel hose or injectors from injector gallery. Turn ignition on. Ensure fuel does not drip from injector(s). Replace any injector(s) that drip fuel. Perform FINAL CHECK.