Trouble Code Identification

NOTE: Trouble codes retrieved from PCM/TCM may be related to either engine or transmission. Transmission-related codes are covered in this article. For engine-related codes, see appropriate G - TESTS W/ CODES article in the ENGINE PERFORMANCE section below. See TROUBLE CODE IDENTIFICATION table to determine if code is transmission or engine related.

TESTS W/CODES - 2.2L (for S10 Pickup)
TESTS W/CODES - 4.3L (for all other models)

The system codes indicate failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of the control module. Code 51 indicates PROM is installed improperly or has failed.
Code 55 indicates PCM/TCM has failed and must be replaced. If the condition is still not corrected after replacing PCM/TCM, the cause may be as follows.

An incorrect PCM/TCM or PROM application may cause a malfunction, which may or may not set a code.
The PCM/TCM connector may be the problem. Connector terminals may have to be removed from the connector to be properly checked.
PROM failure. Although the PROM rarely fails, it could be the cause of the problem.
Replacement PCM/TCM may be faulty.
Intermittent problem. Make a careful physical inspection of affected sensor/circuit.
A shorted solenoid, relay, or harness may be the cause of PCM/TCM failure. Use Short Circuit Tester (J-34636) to check for short circuits.

TROUBLE CODE IDENTIFICATION

Code

Probable Cause

12 ⁽¹⁾

No Engine Speed Sensor Reference Pulse

13 ⁽¹⁾

Open Oxygen Sensor Circuit

Engine Shutoff Solenoid Circuit Fault

14 ⁽¹⁾

CTS Voltage Low (Sensor Or Signal Line Grounded)

ECT Sensor Circuit Low (High Temp. Indicated)

15 ⁽¹⁾

CTS Voltage High (Sensor Or Signal Line Open)

ECT Sensor Circuit High (Low Temp. Indicated)

16 ⁽¹⁾

VSS Buffer Fault (4.3L)

16 ⁽²⁾

Transmission Output Speed Signal Low

Vehicle Speed Sensor Buffer Fault

High Resolution Circuit Fault

Pump Cam Reference Pulse Error

Crankshaft Position Reference Error

21 ⁽¹⁾

TP Sensor Voltage High (Open Ckt Or Misadjusted TP Sensor)

Accelerator Pedal Position No. 1 Circuit High

22 ⁽¹⁾

TP Sensor Voltage Low (Circuit Grounded)

Accelerator Pedal Position No. 1 Circuit Low

23 ⁽¹⁾

Intake Air Temperature Low

Accelerator Pedal Position No. 1 Circuit Range Fault

24 ⁽³⁾

Vehicle Speed Sensor Transmission Output Signal

25 ⁽¹⁾

Intake Air Temperature Sensor Voltage Low

Accelerator Pedal Position No. 2 Circuit High

Accelerator Pedal Position No. 2 Circuit Low

Accelerator Pedal Position No. 2 Circuit Range Fault

28 ⁽⁴⁾

Trans. Range Pressure Switch (4L60E/4L80E)

Glow Plug Relay Circuit Fault

31 ⁽¹⁾

Engine Speed Control Governor (5.7L "G" Van)

EGR Control Pressure/BARO Sensor Circuit Low (High Vacuum)

32 ⁽¹⁾

EGR Circuit Error

33 ⁽¹⁾

MAP Voltage High (Circuit Open Or Short To Voltage)

EGR Control Pressure/BARO Sensor Circuit High (Low Vacuum)

34 ⁽¹⁾

MAP Voltage Low (Circuit Open Or Short To Ground)

Injection Timing Stepper Motor Circuit Fault

35 ⁽¹⁾

IAC System Fault

Injection Pulse Width Error (Response Time Short)

Injection Pulse Width Error (Response Time Long)

37/38 ⁽⁴⁾

TCC Brake Switch On/Off (4L60E/4L80E)

39 ⁽⁴⁾

TCC Stuck Off (4L80E)

Brake Switch Circuit Fault

42 ⁽¹⁾

EST Circuit Fault

Fuel Temperature Circuit Low (High Temp. Indicated)

43 ⁽¹⁾

Knock Sensor Circuit Fault

Fuel Temperature Circuit High (Low Temp. Indicated)

44 ⁽¹⁾

Lean Exhaust Indicated

EGR Pulse Width Error

45 ⁽¹⁾

Rich Exhaust Indicated

EGR Vent Error

MIL (SERVICE ENGINE SOON) Circuit Fault

IAT Sensor Circuit Low (High Temp. Indicated)

IAT Sensor Circuit High (Low Temp. Indicated)

SERVICE THROTTLE SOON Light Circuit Fault

51 ⁽¹⁾

PROM Error (Faulty Or Incorrect PROM)

52 ⁽¹⁾

PROM/CALPAC Error (Faulty/Incorrect PROM/CALPAC)

52 ⁽⁴⁾

System Voltage High (4L60E/4L80E)

53 ⁽³⁾

System Voltage High

54 ⁽¹⁾

Fuel Pump Circuit Voltage Low

PCM Fuel Circuit Error

55 ⁽¹⁾

ECM/PCM/VCM Error

Injection Pump Calibration Resistor Error

PCM 5-Volt Shorted

58 ⁽⁴⁾

Trans. Fluid Temp. High (4L60E/4L80E)

59 ⁽⁴⁾

Trans. Fluid Temp. Low (4L60E/4L80E)

Turbo Boost Sensor Circuit High

Turbo Boost Sensor Circuit Low

Accelerator Pedal Position No. 3 Circuit High

Accelerator Pedal Position No. 3 Circuit Low

63/64 ⁽⁴⁾

BARO Signal High/Low (4L80E)

Accelerator Pedal Position No. 3 Circuit Range Fault

66 ⁽⁴⁾

3-2 Control Solenoid Circuit Fault (4L60E)

67 ⁽⁴⁾

TCC Solenoid Circuit Check (4L60E)

68 ⁽⁴⁾

Overdrive Ratio Error (4L80E)

69 ⁽⁴⁾

Torque Converter Clutch Stuck On (4L60E/4L80E)

Set/Coast Switch Fault

71 ⁽⁴⁾

Camshaft Sensor Circuit Low (4L80E)

72 ⁽⁴⁾

VSS Circuit Loss (4L60E/4L80E) Transmission Output Signal

73 ⁽⁴⁾

Pressure Control Solenoid (4L60E/4L80E) (Current Error)

74 ⁽⁴⁾

Trans. Input Speed Error (4L80E)

75 ⁽⁴⁾

System Voltage Low (4L60E/4L80E)

Resume/Accel Switch Fault

Wastegate Solenoid Fault

79 ⁽⁴⁾

Trans. Fluid Temp. High (4L60E/4L80E)

81 ⁽⁴⁾

Trans. 2-3 Error (4L60E/4L80E)

82 ⁽⁴⁾

Trans. 1-2 Error (4L60E/4L80E)

83 ⁽⁴⁾

TCC Solenoid Circuit Fault (4L80E)

Accelerator Pedal Position Circuit Fault

85 ⁽⁴⁾

Undefined Gear Ratio (4L80E)

86 ⁽⁴⁾

Low Gear Ratio Error (4L80E)

87 ⁽⁴⁾

High Gear Ratio Error (4L80E)

TDC Offset Error

Cylinder Balance Fault No. 1 Cylinder

Cylinder Balance Fault No. 2 Cylinder

Cylinder Balance Fault No. 3 Cylinder

Cylinder Balance Fault No. 4 Cylinder

Cylinder Balance Fault No. 5 Cylinder

Cylinder Balance Fault No. 6 Cylinder

Cylinder Balance Fault No. 7 Cylinder

Cylinder Balance Fault No. 8 Cylinder

Accelerator Pedal Position No. 2 (5-Volt Reference Fault)

P0107 ⁽¹⁾

MAP Signal Voltage Low (4.3L)

P0108 ⁽¹⁾

MAP Signal Voltage High (4.3L)

P0122 ⁽¹⁾

TP Sensor Circuit Signal Voltage Low

P0123 ⁽¹⁾

TP Sensor Circuit Signal Voltage High

P0131 ⁽¹⁾

HO2S Circuit Low Signal Voltage

P0132 ⁽¹⁾

HO2S Circuit High Signal Voltage

P0139 ⁽¹⁾

HO2S Circuit Open (4.3L)

P0171 ⁽¹⁾

Fuel Trim Lean (Lean Exhaust)

P0172 ⁽¹⁾

Fuel Trim Rich (Rich Exhaust)

P0320 ⁽¹⁾

Ignition Control Error (4.3L)

P0321 ⁽¹⁾

Spark Reference Circuit

P0327 ⁽¹⁾

Knock Sensor Circuit Grounded (4.3L)

P0328 ⁽¹⁾

Knock Sensor Circuit Open (4.3L)

P0342 ⁽¹⁾

Cam Signal Circuit

P0400 ⁽¹⁾

EGR Error

P0500 ⁽¹⁾

VSS Error (4.3L)

P1222 ⁽¹⁾

Fuel Pump Voltage Low

P1530 ⁽¹⁾

A/C Head Pressure Switch Circuit

P1531 ⁽¹⁾

Low A/C Refrigerant Charge

P1558 ⁽¹⁾

Cruise System Problem

P1561 ⁽¹⁾

Cruise Vent Solenoid Circuit

P1562 ⁽¹⁾

Cruise Vacuum Solenoid Circuit

P1565 ⁽¹⁾

Cruise Servo Position Sensor Circuit

P1567 ⁽¹⁾

Cruise Switches Circuit

P1568 ⁽¹⁾

Cruise System Problem

P1571 ⁽⁴⁾

Traction Control Desired Torque Out Of Range

P1573 ⁽⁴⁾

Traction Control Loss Of ABS/TCS Serial Data

P1599 ⁽¹⁾

Cruise Power Management

P1623 ⁽¹⁾

PROM Error

P1632 ⁽¹⁾

System Voltage High (4.3L)

⁽¹⁾	Gasoline engine code covered in TESTS W/CODES - 2.2L (for S10 Pickup) or TESTS W/CODES - 4.3L (for all other models).

⁽²⁾	Models equipped with 4L60E transmission.

⁽³⁾	Common engine/transmission code. See TESTS W/CODES - 2.2L (for S10 Pickup) or TESTS W/CODES - 4.3L (for all other models).

⁽⁴⁾	Transmission code covered in this article.