Trouble Code Identification
- The DEC system codes indicate a failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of the ECM. Code 51 indicates that PROM is improperly installed or has failed.
- Code 52 indicates that the ECM has failed and must be replaced. If the ECM is replaced and the condition was not corrected, the following may be the cause:
- An incorrect ECM or PROM application may cause a malfunction and may, or may not, set a code.
- The ECM connector may be the problem. Connector terminals may have to be removed from the connector to properly check them.
- PROM failure. Although the PROM rarely fails, it could be the cause of the problem.
- Replacement ECM may be faulty.
- Intermittent problem. Make a careful physical inspection of affected sensor/circuit.
- A shorted solenoid, coil relay, or harness may cause an ECM to fail and a replacement ECM to fail when it is installed. Use Short Circuit Tester (J-34636 ), to check for short circuits.
TROUBLE CODE IDENTIFICATION
| Code & (Affected Circuit) | Probable Cause |
|---|---|
| 12 (Engine Speed Sensor) | No engine speed sensor reference pulse to ECM. |
| 14 (CTS High Temp. Indication) | Sets if sensor or signal line becomes grounded for 5 minutes. |
| 15 (CTS Low Temp. Indication) | Sets if sensor, connections, or wires open for 5 minutes. |
| 21 (TPS Signal Voltage High) | Open circuit or misadjusted TPS. Engine must run for 30 seconds at curb idle, before code will set. |
| 22 (TPS Signal Voltage Low) | TPS circuit grounded. Engine must run for 2 minutes at 1250 RPM or higher before code will set. |
| 23 (TPS Not Calibrated) | Voltage not between .25-1.3 volts at curb idle. Engine must run for 30 seconds at curb idle, before code will set. |
| 24 (Vehicle Speed Sensor) | VSS circuit open or grounded. Vehicle must operate at road speed for 10 seconds before code will set. |
| 31 (MAP Sensor Signal Voltage Low) | Engine must run at curb idle for 10 seconds before code will set. |
| 32 (EGR Loop Error) | EGR vacuum circuit has improper vacum signal. Vehicle must operate at 30 MPH for 10 seconds before code will set. |
| 33 (MAP Sensor Signal Voltage High) | Engine must run at curb idle for 10 seconds before code will set. |
| 51 (PROM Fault) | Improperly installed or faulty PROM. 10 seconds must elapse before code will set. |
| 52 (ECM Fault) | Fault in ECM circuit. 10 seconds must elapse before code will set. |
| 53 (5-Volt Reference Overload) | Grounded 5-volt reference signal. 10 seconds must elapse before code will set. |