Reading Trouble Codes

The control module 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 control module and sensor/solenoid connector terminals with a digital voltmeter. Some models REQUIRE a scan tester to pull trouble codes. See SCAN TESTER DATA 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.

DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION

DTC	Probable Cause
13	Open Oxygen Sensor Circuit
14	Coolant Sensor Signal Voltage Low
15	Coolant Sensor Signal Voltage High
16	VSS Buffer Fault
21	TPS Signal Voltage High
22	TPS Signal Voltage Low
24	VSS - "C" & "K" Series Except M/T
24	VSS Transmission Output Signal - With A/T
24	VSS - With M/T
28	Transmission Range Pressure Switch
31	Engine Speed Governor - "G" Series
32	EGR Circuit Error Backpressure EGR With Solenoid
32	EGR Circuit Error With EVRV Solenoid
32	EGR Ckt Error - "C", "G", "K" Series W/ Linear EGR
33	MAP Sensor Signal Voltage High
34	MAP Sensor Signal Voltage Low
35	Idle Speed Error
36	Idle Speed Actuator FaulT - A/T
37	TCC Brake Switch On/Off
38	TCC Brake Switch On/Off
39	TCC Stuck Off - 4L80-E Transmission
42	Ignition Control
43	Knock Sensor Without Spark Module (Dual Sensors)
43	Knock Sensor Without Spark Module (Single Sensor)
43	Knock Sensor With Spark Control Module
44	Lean Exhaust Indicated
45	Rich Exhaust Indicated
51	PROM Error (Faulty Or Incorrect PROM)
52	Faulty CALPAK
52/53	System Voltage High
54	Fuel Pump Circuit
55	ECM/PCM Error
58	Transmission Fluid Temperature High
59	Transmission Fluid Temperature Low
66	3-2 Control Solenoid Ckt Fault 4L60-E Transmission
67	TCC Solenoid Circuit Check - 4L60-E Transmission
68	Overdrive Ratio Error - 4L80-E Transmission
69	Torque Converter Clutch Stuck On 4L60-E Transmission
69	Torque Converter Clutch Stuck On 4L80-E Transmission
72	VSS Circuit Loss Transmission Output Signal
73	Pressure Control Solenoid (Current Error)
74	Transmission Input Speed Error 4L80-E Transmission
75	System Voltage Low
79	Transmission Fluid Temperature High
81	Transmission 2-3 Error
82	Transmission 1-2 Error
83	TCC Solenoid Circuit Fault
85	Undefined Gear Ratio
86	Low Gear Ratio Error
87	High Gear Ratio Error

NOTE: On models not using "P" series codes, Code 12 should always exist when DLC test terminal is grounded with key on and engine off, but it may not be indicated by all makes of scan tester.