GM OBD I Diagnostic Trouble Code Definitions

Chevy S10/GMC S15 OBD I Trouble Code Definitions
Code Description
12 System Check
13 Oxygen Sensor Circuit
14 Engine Coolant Temperature (ECT) High Temperature Indicated
15 Engine Coolant Temperature (ECT) Sensor Signal Voltage High
16 Transmission Speed Error
21 TPS Signal Voltage High
22 TPS Signal Voltage Low
23 MAT (Manifold Air Temperature) Signal Voltage High
24 Vehicle Speed Sensor (VSS) Signal Voltage High
25 MAT (Manifold Air Temperature) Signal Voltage Low
26 Quad Driver 1 Fault (4.3L M/T only)
27 Quad Driver 2 Fault (4.3L M/T only)
28 Transmission Pressure Switch Manifold Range Circuit Problem
32 EGR System Failure
33 MAP Sensor Signal Voltage High
34 MAP Sensor Signal Voltage Low
35 Idle Speed Error
37 Brake Switch Stuck On (4L60-E A/T only)
39 Knock Sensor Circuit Shorted (4.3L M/T Only)
42 Electronic Spark Timing (EST) Fault
43 Electronic Spark Control (ESC) Fault
44 Lean Exhaust
45 Rich Exhaust
51 PROM/MEM-CAL Fault
51 System Voltage High (Charging System Problem)
54 Fuel Pump Circuit
54 Faulty ECM/PCM/VCM
Reading The On/Off Flashes Of The Check Engine LIght (How to Retrieve GM OBD I Diagnostic Trouble Codes)

More GM 2.8L Tutorials

To see all of the 2.8L S10/S15 specific articles, go to: GM 2.8L Index of Articles.

Here's a sample of the articles you'll find in the Index of Articles:

  1. Vacuum Hose Routing Diagram 1988 GM 2.8L S10/S15.
  2. How To Test For A Bad Alternator (2.8L V6 S10/S15).
  3. How To Test Engine Compression (2.8L S10 Pickup/Blazer).
  4. How To Bench Test The Starter Motor.
  5. How To Test The Starter Motor On the Car (Step by Step).
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