Reading Trouble Codes

NOTE: Trouble codes retrieved from ECM/PCM/VCM may be related to either engine or transmission. For engine-related codes, use this article. For transmission-related codes, see G - TRANS. TESTS W/ CODES article in this section. To identify whether codes relate to transmission or engine, see TROUBLE CODE IDENTIFICATION table.

The ECM stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Read trouble codes by counting Malfunction Indicator Light (MIL) flashes or with diagnostic scan tester connected to the Data Link Connector (DLC). The tester is faster, and capable of reading information which would require testing individual ECM and sensor/solenoid connector terminals with a digital voltmeter. See SCAN TESTER DATA table and SCAN TESTER USAGE .

NOTE: When using a scan tester, there is a time delay between serial data updates. For instantaneous response, a digital voltmeter must be used.

If scan tester is not available, MIL flashes can be read by grounding DLC terminal with ignition on and engine off. For example, FLASH, FLASH, pause, FLASH, longer pause, indicates Code 21. The first series of flashes are the first digit of trouble code. The second series of flashes are the second digit of trouble code. Trouble codes are displayed starting with the lowest code. Each code is displayed 3 times and will continue as long as DLC is grounded.

NOTE: Trouble codes will be recorded at various operating times. Some codes require sensor or switch operation for 5 seconds and others may require longer under certain conditions. Some codes may not set in a service bay operational mode.

TROUBLE CODE IDENTIFICATION

Code

Probable Cause

12 ⁽¹⁾

No Engine Speed Sensor Reference Pulse

13 ⁽¹⁾

Open Oxygen Sensor Circuit

14 ⁽¹⁾

CTS Voltage Low (Sensor Or Signal Line Grounded)

15 ⁽¹⁾

CTS Voltage High (Sensor Or Signal Line Open)

16 ⁽¹⁾

System Voltage High/Low (3.8L) ⁽²⁾ Transmission Speed Error

17 ⁽¹⁾

RPM Signal Problem (3.8L)

18 ⁽¹⁾

Cam/Crank Error (3.8L)

21 ⁽¹⁾

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

22 ⁽¹⁾

TP Sensor Voltage Low (Circuit Grounded)

23 ⁽¹⁾

Intake Air Temperature Sensor Voltage High

24 ⁽³⁾

Vehicle Speed Sensor Circuit Open Or Grounded

25 ⁽¹⁾

Intake Air Temperature Sensor Voltage Low

26 ⁽¹⁾

Quad-Driver "A" Fault (3.8L) Quad-Driver 1 Fault (4.3L M/T "S" & "T" Pickup)

27 ⁽¹⁾

Quad-Driver 2 Fault (4.3L M/T "S" & "T" Pickup)

28 ⁽⁴⁾

Pressure Switch Manifold Range Circuit Open Or Shorted

31 ⁽¹⁾

Park/Neutral Switch Circuit (3.8L) Turbocharger Wastegate Overboost (4.3L Turbo) Engine Speed Control Governor (5.7L "G" Van) Turbocharger Wastegate Overboost (4.3L Turbo)

32 ⁽¹⁾

EGR Error (Improper Vacuum Signal)

33 ⁽¹⁾

MAP Voltage High (Circuit Open Or Short To Voltage)

34 ⁽¹⁾

MAP Voltage Low (Circuit Open Or Short To Ground) MAF Sensor Signal Voltage Low (3.8L)

35 ⁽¹⁾

IAC System Fault

36 ⁽¹⁾

Shift Control Problem (3.8L)

37 ⁽⁴⁾

Brake Switch Stuck On (4L60-E)

38 ⁽¹⁾

Brake Switch Circuit (3.8L) Knock Sensor Circuit Open (4.3L M/T "S" & "T" Pickup)

38 ⁽⁴⁾

Brake Switch Stuck Off (4L60-E)

TCC Stuck Off (⁽¹⁾ 3.8L & ⁽⁴⁾ 4L80-E) ⁽¹⁾ Knock Sensor Circuit Shorted (4.3L M/T "S" & "T" Pickup)

41 ⁽¹⁾

Cam Sensor Circuit (3.8L)

42 ⁽¹⁾

EST Circuit Fault

43 ⁽¹⁾

ESC Fault

44 ⁽¹⁾

Lean Exhaust Indicated

45 ⁽¹⁾

Rich Exhaust Indicated

51 ⁽¹⁾

Improperly Installed/Faulty PROM/MEM-CAL

52 ⁽⁴⁾

Long System Voltage High (4L60-E)

52 ⁽¹⁾

Fuel CALPAC Missing

53 ⁽³⁾

System Voltage High (Charging System Problem)

53,54 & 55⁽¹⁾

EGR Fault (3.8L)

54 ⁽¹⁾

Fuel Pump Circuit Voltage Low

55 ⁽¹⁾

Faulty ECM/PCM/VCM

56 ⁽¹⁾

Quad-Driver "B" Fault (3.8L)

58 ⁽⁴⁾

TTS High Temperature (Sensor Or Signal Line Grounded)

59 ⁽⁴⁾

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

61 ⁽¹⁾

Cruise Vent Solenoid (3.8L)

62 ⁽¹⁾

Cruise Vacuum Solenoid (3.8L)

63 ⁽¹⁾

Cruise System Problem (3.8L)

65 ⁽¹⁾

Cruise Servo Position (3.8L)

66 ⁽¹⁾

Low A/C Refrigerant Charge (3.8L)

66 ⁽⁴⁾

3-2 Control Solenoid Fault (4L60-E)

67 ⁽⁴⁾

TCC Solenoid Circuit Fault (4L60-E)

67 ⁽¹⁾

Cruise Engage Switches (3.8L)

68 ⁽⁴⁾

Overdrive Ratio Error (Engine RPM Greater Than Input Speed)

68 ⁽¹⁾

Cruise System Problem (3.8L)

69 ⁽⁴⁾

Torque Converter Stuck On (4L60-E)

69 ⁽¹⁾

A/C Head Pressure Switch (3.8L)

72 ⁽⁴⁾

VSS Signal Loss (4L60-E)

73 ⁽⁴⁾

Force Motor (Pressure Control Solenoid) Error

75 ⁽⁴⁾

System Voltage Low (Charging System Problem)

79 ⁽⁴⁾

Transmission Fluid Temperature High (4L60-E)

81 ⁽⁴⁾

QDM Solenoid "B" (2nd-3rd) Current Error

82 ⁽⁴⁾

QDM Solenoid "A" (1st-2nd) Current Error

83 ⁽⁴⁾

QDM TCC Solenoid Circuit Fault (4L80-E)

85 ⁽⁴⁾

Undefined Gear Ratio (4L80-E)

86 ⁽⁴⁾

Low Gear Ratio (4L80-E)

87 ⁽⁴⁾

High Gear Ratio (4L80-E)

⁽¹⁾	Engine code covered in this article.

⁽²⁾	Models equipped with 4L60-E transmission, and 4.3L "S" and "T" series utility vehicles with man. trans.

⁽³⁾	Common engine and transmission code covered in this article.

⁽⁴⁾	Transmission code. For transmission code diagnosis, see appropriate AUTO TRANS DIAGNOSIS article in AUTO TRANS DIAGNOSIS section.

NOTE: Trouble code charts should only be used if Malfunction Indicator Light (MIL) is illuminated (indicating a current problem exists). Exceptions are Code 13, 15, 24, 44 and 45 charts, which may be used to help diagnose intermittent codes. Anytime Code 51, 52 or 55 is displayed with another code, start with 50-series code first and proceed to lower numbered codes.