NOTE: Trouble codes retrieved from ECM may be either engine or transmission related. Only engine-related codes are covered in this article. For transmission-related codes, see TESTS W/CODES - TRANSMISSION article in ENGINE PERFORMANCE section. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table to determine if code is engine or transmission related.

The DEC system codes indicate failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of ECM. DTC 51 indicates PROM is either improperly installed or has failed.
DTC 52 indicates ECM has failed and must be replaced. If condition is still not corrected after replacing ECM, the following may be the cause:
- An incorrect ECM or PROM application may cause a malfunction, which may or may not set a code.
- The ECM connector may be the problem. Connector terminals may have to be removed from connector to be checked properly.
- 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 be the cause of ECM failure. Use Short Circuit Tester (J-34636) to check for short circuits.

DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

Code

Probable Cause

12 ⁽¹⁾

No Engine Speed Sensor Reference Pulse

14 ⁽¹⁾

CTS Voltage Low (Sensor Or Signal Line Grounded)

15 ⁽¹⁾

CTS Voltage High (Sensor, Connections, Or Wires Open)

16 ⁽¹⁾

Transmission Output Speed Voltage Low

21 ⁽¹⁾

TPS Voltage High (Open Circuit Or Misadjusted TPS)

22 ⁽¹⁾

TPS Voltage Low (Circuit Grounded)

23 ⁽¹⁾

TPS Not Calibrated (.25-1.3 Volts At Curb Idle)

24 ⁽¹⁾

Vehicle Speed Sensor Circuit Open Or Grounded

Pressure Switch Manifold Range Circuit Open Or Shorted

31 ⁽¹⁾

MAP Voltage Low (Circuit Open Or Shorted To Ground)

32 ⁽¹⁾

EGR Error (Improper Vacuum Signal)

33 ⁽¹⁾

MAP Voltage High (Circuit Open Or Shorted To Ground)

TCC Stuck Off (Faulty TCC Solenoid)

51 ⁽¹⁾

Improperly Installed/Faulty PROM

52 ⁽¹⁾

ECM Fault

53 ⁽¹⁾

Voltage Reference Overload

TTS High Temperature (Sensor Or Signal Line Grounded)

TTS Low Temperature (Sensor, Connections, Or Wires Open)

Overdrive Ratio Error (Engine RPM Greater Than Input Speed)

Force Motor Commanded Amperage Differs From Return

System Voltage Low (Charging System Problem)

QDM Solenoid "B" Monitored Voltage Differs From Commanded

QDM Solenoid "A" Monitored Voltage Differs From Commanded

QDM TCC Monitored Voltage Differs From Commanded

Undefined Gear Ratio (Input Or Output Sensor Failure)

Shift Solenoid "B" Stuck On (Commanded Gear Not Engaged)

Shift Solenoid "B" Stuck Off (Commanded Gear Not Engaged)

⁽¹⁾	Code is engine related. Engine related codes are covered in this article. For information on transmission related codes, see TESTS W/CODES - TRANSMISSION article in this section.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Trouble Code Identification

Use the Manual With the Right Hardware

When to See a Mechanic

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