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HOMESERVICE MANUALSCHEVROLET1993SPORTVAN G30, VAN PASSENGER, 7.4 NREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 15 (ENGINE CONTROLS - TESTS W/CODES - 5.0L)SELF-DIAGNOSTIC SYSTEMREADING TROUBLE CODES
1993 Chevrolet Sportvan G30, Van Passenger, 7.4 N

Reading Trouble Codes

1993 Chevrolet Sportvan G30, Van Passenger, 7.4 NSECTION Reading Trouble Codes
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1994 GMC Vandura, 1994 GMC Rally, 1994 GMC Pickup, 1994 Chevrolet Sportvan, and 1994 Chevrolet Pickup. However, it is still accessible from the selected car via links, so may be relevant.
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 appropriate G - ELECTRONIC TRANSMISSION TESTS W/ CODES article in this section. See below. To identify whether codes relate to transmission or engine, see TROUBLE CODE IDENTIFICATION table.
  • G - TESTS W/CODES - ELECTRONIC TRANSMISSION (for "C" & "K" Series)
  • AUTO TRANS DIAGNOSIS - 4L60-E & 4L80-E (For "G" & "P" Series)

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 No Engine Speed Sensor Reference Pulse
13 Open Oxygen Sensor Circuit
14 CTS Voltage Low (Sensor Or Signal Line Grounded)
15 CTS Voltage High (Sensor Or Signal Line Open)
21 TP Sensor Voltage High (Open Circuit Or Misadjusted TP Sensor)
22 TP Sensor Voltage Low (Circuit Grounded)
23 Intake Air Temperature Low
24 (1) Vehicle Speed Sensor Circuit
25 Intake Air Temperature Sensor Voltage Low
28 (2) Transmission Range Pressure Switch
32 EGR Circuit
33 MAP Voltage High (Circuit Open Or Short To Voltage)
34 MAP Voltage Low (Circuit Open Or Short To Ground)
35 IAC System Fault
36 Idle Speed Control Actuator "C", "K" A/T
37 (2) Brake Switch Stuck Off (4L60E/4L80E)
38 (2) Brake Switch Stuck Off (4L60E/4L80E)
39 (2) TCC Stuck Off
42 EST Circuit Fault
43 Knock Sensor Circuit Fault
44 Lean Exhaust Indicated
45 Rich Exhaust Indicated
51 PROM Error (Faulty/Incorrect PROM)
52 (2) Long System Voltage High (4L60E/4L80E)
52 PROM/CALPAC Error (Faulty/Incorrect PROM/CALPAC)
53 (1) System Voltage High (Charging System Problem)
54 Fuel Pump Circuit Voltage Low
55 ECM/PCM/VCM Error
58 (2) TFT Sensor Circuit Low
59 (2) TFT Sensor Circuit High
66 (2) 3-2 Control Solenoid Fault (4L60E)
67 (2) TCC Solenoid Circuit Fault (4L60E)
68 (2) Overdrive Ratio Error (Engine RPM Greater Than Input Speed)
69 (2) Torque Converter Stuck On (4L60E/4L80E)
72 (2) VSS Signal Loss (4L60E/4L80E)
73 (2) Force Motor (Pressure Control Solenoid) Error
75 (2) System Voltage Low (Charging System Problem)
79 (2) Transmission Fluid Temperature High (4L60E/4L80E)
81 (2) 2-3 Shift Solenoid Circuit Fault (4L60E/4L80E)
82 (2) 1-2 Shift Solenoid Circuit Fault (4L60E/4L80E)
83 (2) QDM TCC Solenoid Circuit Fault (4L80E)
85 (2) Undefined Gear Ratio (4L80E)
86 (2) Low Gear Ratio (4L80E)
87 (2) High Gear Ratio (4L80E)
(1) Common gasoline engine and transmission code covered in this article.
(2) Transmission code. For automatic transmission code diagnosis, see appropriate G - ELECTRONIC TRANSMISSION TESTS W/ CODES article in this section. See G - TESTS W/CODES - ELECTRONIC TRANSMISSION (for "C" & "K" Series) or AUTO TRANS DIAGNOSIS - 4L60-E & 4L80-E (For "G" & "P" Series).
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.
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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.