TROUBLE CODE DEFINITION
| Code | System Affected | Probable Cause |
|---|---|---|
| 12 | System Normal | System Normal |
| 13 | O2 Sensor | Sensor or Circuit ECM |
| 14A (1) | Coolant Temperature Sensor | Sensor or Circuit, ECM |
| 14B (2) | Coolant Temperature Sensor | Sensor or Circuit, ECM |
| 21A | TPS Signal (High) | TPS, ECM |
| 21B | TPS Signal (Low) | TPS, ECM |
| 23A | MAT Circuit (Low) | Sensor or Circuit, ECM |
| 23B | MAT Circuit (High) | Sensor or Circuit, ECM |
| 24 | Vehicle Speed Sensor | Sensor or Circuit, ECM |
| 32 | EGR System | EGR Valve, Wiring, Circuit, EGR Solenoid, EGR Filter, EVRV, ECM |
| 33A | MAP Sensor Signal (High) | Sensor or Circuit, ECM |
| 33B | MAP Sensor Signal (Low) | Sensor or Circuit, ECM |
| 42 | Electronic Spark Timing | Wiring Circuit, Ignition Module, ECM |
| 43 | Electronic Spark Control | Knock Sensor or Circuit, ESC Module or ECM |
| 44 | O2 Sensor (Lean) | Injectors, Fuel Pressure, Exhaust Leaks, O2 Sensor or Circuit, MAP Sensor or ECM |
| 45 | O2 Sensor (Rich) | Injectors, Fuel Pressure, O2 Sensor or Circuit, MAP Sensor, TPS, Canister Purge, Ignition Shielding, ECM |
| 51 | PROM Error | PROM or ECM |
| (1) High temperature indicated by temperature sensor. (2) Low temperature indicated by temperature sensor. | ||
| (1) | High temperature indicated by temperature sensor. |
| (2) | Low temperature indicated by temperature sensor. |
TROUBLE CODE IDENTIFICATION
DIAGNOSTIC CIRCUIT CHECK
| Scan Position | (1) Data Value |
|---|---|
| A/C | No (Yes W/ A/C Requested) |
| A/C Clutch | Off (On W/ A/C Requested) |
| Air Control Solenoid | Off |
| Air Fuel Ratio | 0-25.5:1 |
| Battery | 13-15 Volts |
| BARO | Voltage Varies Depending On Altitude |
| BLE (Block Learn Enable) | Yes |
| BLM (Block Learn Memory) | 116-145 Counts |
| Block Learn Cell | 1 |
| BPW (Base Pulse Width) | 0-499.9 Milliseconds |
| Canister Purge | Off |
| Coolant Temperature | 185-221°F (85-105°C) |
| EGR Solenoid | Off |
| EST (Electronic Spark Timing) | Yes |
| IAC (Idle Air Control) | 1-50 Counts |
| Idle Throttle | Yes |
| INT (Integrator) | Varied 108-154 Counts |
| Knock Retard | 0-45 Degrees |
| MAP (Manifold Absolute Pressure) | (2) 1-2 Volts |
| MAT (Manifold Air Temperature) | (3) 50-199°F (10-93°C) |
| Open/Closed Loop | Closed Loop |
| Oxygen Sensor | (3) .1-1.0 Volt |
| PARK/NEUTRAL Position | Park/Neutral |
| Power Steering Switch | Normal |
| Prom Identification | 0-65535 |
| RPM | (4) (5) RPM Is Controlled By ECM |
| Rich/Lean Flag | Varies |
| Second Throttle Solenoid | Off (On Above 5000 RPM) |
| Shift Light | Off |
| Spark Advance | Varies |
| Throttle Angle | Zero Percent At Idle |
| TPS (Throttle Position Sensor) | .50-.1.25 Volts |
| VSS (Vehicle Speed Sensor) | 0 MPH |
| (1) With engine idling at normal operating temperature, in Park or Neutral, system in closed loop and all accessories off. (2) Voltage varies with vacuum and barometric pressure. (3) Voltage varies with exhaust temperature. (4) Plus or minus 50 RPM from desired RPM (A/T). (5) Plus or minus 100 RPM from desired RPM (M/T). | |
| (1) | With engine idling at normal operating temperature, in Park or Neutral, system in closed loop and all accessories off. |
| (2) | Voltage varies with vacuum and barometric pressure. |
| (3) | Voltage varies with exhaust temperature. |
| (4) | Plus or minus 50 RPM from desired RPM (A/T). |
| (5) | Plus or minus 100 RPM from desired RPM (M/T). |
SCAN DATA
Diagnostic circuit check will identify problem created by Electronic Engine Control System (EECS) malfunction. It is the starting point for diagnosis. This check will direct you to the next logical step in diagnosing the complaint.
After completing diagnostic circuit check and finding on-board diagnostics functioning properly with no trouble codes displayed, use appropriate SCAN DATA table for comparison.
Data values must be taken under these conditions
- Engine at normal operating temperature.
- Engine running at idle.
- Vehicle in Park or Neutral.
- System in closed loop.
Note. The values are an average of displayed values recorded from normal operating vehicles. Values represent what a normal functioning system would typically display.
Note. Only parameters supplied by manufacturer are used in this article. If a scan tester reads other parameters, values are not recommended by manufacturer for diagnostic use. A scan tester displaying faulty data should not be used, or misdiagnosis will occur. Report problem to scan tester manufacturer.
Note. Test numbers refer to numbers on diagnostic chart.
- This step checks if ECM can provide a ground path for CHECK ENGINE light. This is a bulb check.
- This step checks if ECM can perform internal diagnostics.
- This step checks if ECM can supply serial data for scan tester.
- This step verifies scan data.
- This step checks whether ECM or electrical system is cause of no start.
- This step checks ECM memory for codes to aid in diagnosis.
Scheme 71
Diagnostic Aids
- Engine Runs Okay - Check for faulty light bulb, open in circuit No. A5 or defective gauge fuse. This will result in no oil indicator light, alternator light, seat belt reminder light, etc.
- Engine Cranks, But Will Not Run - Check for continuous battery drain, fuse or fusible link open, ECM ignition fuse open, battery circuits No. B1 and C16 to ECM open, ignition circuit No. A6 to ECM open or poor connection to ECM.
Scheme 72
Scheme 73
Normal scan tester voltage varies between .1-1.0 volt while in closed loop. Code 13 sets in approximately 40 seconds if voltage remains between .35 and .55 volt, but system will enter open loop in approximately 15 seconds. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 74
Scheme 75
Scheme 76
After engine is started, temperature should rise steadily to approximately 194°F (90°C), and then stabilize when thermostat opens. When a Code 14A is set, ECM will turn on engine cooling fan. Code 14A will set if circuit No. D12 is shorted to ground. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 77
Scheme 78
After engine is started, temperature should rise steadily to approximately 194°F (90°C), then stabilize when thermostat opens. Code 14B will set if circuits No. A11 and D12 are open. Check terminals at sensor for good contact. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 79
The scan tester reads throttle position in volts. With ignition on, reading should be less than 1.25 volts with throttle closed. Voltage should increase at a steady rate as throttle is moved toward WOT. An open in circuit No. D2 or a short to voltage in circuit No. D6 will result in Code 21A. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 80
Scheme 81
A scan tester reads throttle position in volts. With ignition on, reading should be less than one volt with throttle closed. Voltage should increase at a steady rate as throttle is moved toward WOT. An open or short to ground in circuits No. A1 or D6 will cause Code 21B to set. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 82
An open in circuit No. D2 or D7 will cause Code 23A to set. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 83
Scheme 84
A Code 23B will set if circuit No. D2 or D7 becomes open or shorted to ground. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 85
A scan tester should indicate vehicle speed whenever vehicle is in motion. A faulty or misadjusted Park/Neutral switch can result in a false Code 24. Use scan tester to check for proper signal while vehicle is in Drive position. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 86
Scheme 87
A sluggish oxygen sensor can cause a false Code 32 to set. If EGR valve passage is restricted, Code 32 may set.
Scheme 88
Scheme 89
An open in circuit No. A11 will cause Code 33A to set. If circuit No. D9 is shorted to voltage, or circuit No. D9 is shorted to circuit No. A1, Code 33A will set. With ignition on and engine off, manifold pressure is equal to atmospheric pressure and voltage will be high. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 90
Scheme 91
An open in circuit No. A11 will cause Code 33A to set. If circuit No. D9 is shorted to voltage, or circuit No. D9 is shorted to circuit No. A1, Code 33A will set. With ignition on and engine off, manifold pressure is equal to atmospheric pressure and voltage will be high. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 92
If Code 42 is stored and hard start problem occurs, problem is probably a grounded EST line (circuit No. D5). For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 93
Scheme 94
Scheme 95
Code 43 can be caused by a faulty connection at knock sensor, ESC module, or ECM. Also check circuit No. D10 for possible open or short to ground. For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 96
Scheme 97
Using scan tester, observe block learn values at different RPM. Scan tester also reads block cells, so block learn values can be checked in each of the cells to determine when Code 44 may have been set. If conditions for Code 44 are present, block learn values will be approximately 150.
- Oxygen sensor pigtail may be mispositioned and contacting exhaust manifold.
- Check for intermittent ground in wire between connector and sensor.
- An output causing ECM to sense a higher than normal vacuum will cause system to go lean. Disconnect MAP sensor. If lean condition is gone, replace sensor.
- Water near the in-tank fuel pump inlet can be delivered to the injectors, causing a lean exhaust. This can set Code 44.
- Fuel system will be lean if pressure is too low. Monitor fuel pressure while driving vehicle at various speeds and/or loads to confirm a problem (if necessary). Verify correct fuel injectors are installed in vehicle.
- If there is an exhaust leak, outside air can be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can also cause a lean condition.
- If the above are okay, problem is a faulty oxygen sensor.
For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
Scheme 98
Code 45 or rich exhaust is most likely caused by one of the following
- Check for fuel-contaminated oil.
- If an open exists in circuit No. B2, HEI-induced electrical noise may result, causing simulated reference pulses to be picked up by ECM. Additional pulses result in a higher than actual engine speed signal. The ECM will increase injector pulse width to match fuel requirements of increased RPM signal. Tachometer will show higher than actual RPM, which can help in diagnosing this problem.
- Check charcoal canister for fuel saturation. If full of fuel, check canister control and hoses.
- An output causing ECM to sense a lower than normal vacuum can cause system to go rich. Disconnecting MAP sensor allows ECM to set a fixed value for the sensor. If rich condition is gone with MAP sensor disconnected, replace sensor.
- An intermittent TPS output causes system to go rich due to a false acceleration indication.
- Inspect oxygen sensor for silicone contamination from fuel, or use of improper RTV sealant. Sensor may have a White powdery coating and result in a high but false signal voltage (rich exhaust). ECM will reduce amount of fuel delivered to engine, causing a severe surge driveability problem.
- Check for EGR valve sticking open at idle, usually accompanied by rough idle or stall complaint, especially at idle.
For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.
