GM Corvette 1984-1996 Repair Guide

Reading Codes

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VEHICLES WITH 12-PIN DIAGNOSTIC CONNECTORS



See Figure 1

The following procedures apply only to 1984-95 vehicles with the 12-pin diagnostic connector only. A scan tool, such as GMs Tech 1® must be used to retrieve diagnostic trouble codes from 1995-96 vehicles with the 16-pin diagnostic connector. When using a scan tool, make sure to carefully follow all instructions supplied by the manufacturer.

Listings of the trouble for the various engine control system covered in this guide are located in this section. Remember that a code only points to the faulty circuit NOT necessarily to a faulty component. Loose, damaged or corroded connections may contribute to a fault code on a circuit when the sensor or component is operating properly. Be sure that the components are faulty before replacing them, especially the expensive ones.

The DLC is also referred to as the Assembly Line Communication Link (ALCL), or Assembly Line Diagnostic Link (ALDL) on earlier vehicles.

The Data Link Connector (DLC) may be located under the dash and sometimes covered with a plastic cover labeled DIAGNOSTIC CONNECTOR.



Click image to see an enlarged view

Fig. Fig. 1: The 12-pin Data Link Connector (DLC) is located under the dash

  1. The diagnostic trouble codes can be read by grounding test terminal B . The terminal is most easily grounded by connecting it to terminal A (internal ECM ground). This is the terminal to the right of terminal B on the top row of the DLC connector.
  2.  
  3. Once the terminals have been connected, the ignition switch must be moved to the ON position with the engine not running.
  4.  
  5. The Service Engine Soon or Check Engine light should be flashing. If it isn't, turn the ignition OFF and remove the jumper wire. Turn the ignition ON and confirm that light is now on. If it is not, replace the bulb and try again. If the bulb still will not light, or if it does not flash with the test terminal grounded, the system should be diagnosed by an experienced driveability technician. If the light is OK, proceed as follows.
  6.  
  7. The code(s) stored in memory may be read through counting the flashes of the dashboard warning lamp. The dash warning lamp should begin to flash Code 12. The code will display as one flash, a pause and two flashes. Code 12 is not a fault code. It is used as a system acknowledgment or handshake code; its presence indicates that the ECM can communicate as requested. Code 12 is used to begin every diagnostic sequence. Some vehicles also use Code 12 after all diagnostic codes have been sent.
  8.  
  9. After Code 12 has been transmitted 3 times, the fault codes, if any, will each be transmitted 3 times. The codes are stored and transmitted in numeric order from lowest to highest.
  10.  

The order of codes in the memory does not indicate the order of occurrence.

  1. If there are no codes stored, but a driveability or emissions problem is evident, the system should be diagnosed by an experienced driveability technician.
  2.  
  3. If one or more codes are stored, record them. Refer to the applicable Diagnostic Code chart in this section.
  4.  
  5. Switch the ignition OFF when finished with code retrieval or scan tool readings.
  6.  

After making repairs, clear the trouble codes and operate the vehicle to see if it will reset, indicating further problems.

VEHICLES WITH 16-PIN DIAGNOSTIC CONNECTORS



On 1994-96 vehicles with a 16-pin diagnostic connector, an OBD-II compliant scan tool must be used to retrieve the trouble codes. Follow the scan tool manufacturer's instructions on how to connect the scan tool to the vehicle and how to retrieve the codes.



Click image to see an enlarged view

Fig. Fig. 2: The 1994-96 vehicles may use either a 12 or 16-pin DLC. If equipped with a 16-pin connector, you MUST use an OBD-II scan tool to retrieve

OBD-I DIAGNOSTIC TROUBLE CODES (DTCS)



The the following code list covers 1984-95 vehicles. The 1994-95 5.7L (VIN P) engine also utilizes some OBD-II codes.

Code 12

No engine RPM reference pulses - System Normal

Code 13

Oxygen Sensor (02S) circuit open - left side on 2 sensor system

Code 14

Engine Coolant Temperature (ECT) sensor -possible circuit high or shorted sensor

Code 15

Engine Coolant Temperature (ECT) sensor -circuit low or open circuit

Code 16

Direct ignition system (DIS), fault line circuit or Distributor ignition system (low resolution pulse) or Missing 2x reference circuit or OPTI-Spark ignition timing system (low resolution pulse) or System voltage out of range

Code 17

Camshaft Position Sensor (OPS) or spark reference circuit error

Code 18

Crank/Cam error

Code 19

Crankshaft Position Sensor (CPS) circuit

Code 21

Throttle Position (TP) sensor circuit - signal voltage out of range, probably high

Code 22

Throttle Position (TP) sensor circuit - signal voltage low

Code 23

Intake Air Temperature (IAT or MAT) sensor circuit temperature out of range, low or Open or grounded M/C solenoid Feedback Carburetor system

Code 24

Vehicle Speed Sensor (VSS) circuit

Code 25

Intake Air Temperature (IAT or MAT) sensor circuit temperature out of range, high

Code 26

Quad-Driver Module #1 circuit or Transaxle gear switch circuit

Code 27

Quad-Driver Module circuit or Transaxle gear switch, probably 2nd gear switch circuit

Code 28

Quad-Driver Module (QDM) #2 circuit or Transaxle gear switch, probably 3rd gear switch circuit

Code 29

Transaxle gear switch, probably 4th gear switch circuit

Code 31

Camshaft sensor circuit fault or Park/Neutral Position (PNP) switch circuit or Wastegate circuit signal

Code 32

Exhaust Gas Recirculation (EGR) circuit fault or Barometric Pressure Sensor circuit low Feedback Carburetor system

Code 33

Manifold Absolute Pressure (MAP) sensor - signal voltage out of range, high or Mass Air Flow (MAE) sensor - signal voltage out of range, probably high

Code 34

- Manifold Absolute Pressure (MAP) sensor - circuit out of range voltage, low or Mass Air Flow (MAF) sensor circuit (gm/sec low)

Code 35

- Idle Air Control (IAC) or idle speed error or Idle Speed Control (ISO) circuit throttle switch shorted Feedback Carburetor system

Code 36

Ignition system circuit error or Transaxle shift problem - 4T60E Transaxle

Code 38

Brake input circuit fault - Torque converter clutch signal

Code 39

Clutch input circuit fault - Torque converter clutch signal

Code 41

Cam sensor or cylinder select circuit fault ignition control (IC) reference pulse system fault or Electronic Spark Timing (EST) circuit open or shorted

Code 42

Electronic Spark Timing (EST) circuit grounded or Ignition Control (IC) circuit grounded or faulty bypass line

Code 43

Knock Sensor (KS) or Electronic Spark Control (ESC) circuit fault

Code 44

Oxygen Sensor (02S), left side on 2 sensor system lean exhaust indicated

Code 45

Oxygen Sensor (02S), left side on 2 sensor system rich exhaust indicated

Code 46

Personal Automotive Security System (PASSKey II) circuit or Power Steering Pressure Switch (PSPS) circuit

Code 47

PCM-BCM data circuit

Code 48

Misfire diagnosis

Code 51

Calibration error, faulty MEM-CAL, ECM or EEPROM failure

Code 52

Engine oil temperature sensor circuit, low temperature indicated or Fuel Calpac missing or Over voltage condition or EGR Circuit fault

Code 53

Battery voltage error or EGR problem or Personal Automotive Security System (PASS-Key) circuit

Code 54

EGR #2 problem or Fuel pump circuit (low voltage) or Shorted mixture control solenoid circuit Feedback Carburetor system

Code 55

A/D Converter error, PCM error or not grounded, EGR #3 problem, Fuel lean monitor, Grounded voltage reference, faulty oxygen sensor or fuel lean Feedback Carburetor system

Code 56

Quad-Driver Module (QDM) #2 circuit or Secondary air inlet valve actuator vacuum sensor circuit signal high 5.7L (VIN J)

Code 57

Boost control problem

Code 58

Vehicle Anti-theft System fuel enable circuit

Code 61

A/C system performance or Cruise vent solenoid circuit fault or Oxygen Sensor (02S) degraded signal or Secondary port throttle valve system fault 5.7L (VIN J) or Transaxle gear switch signal

Code 62

Cruise vacuum solenoid circuit fault or Engine oil temperature sensor, high temperature indicated or Transaxle gear switch signal circuit fault

Code 63

Oxygen Sensor (02S), right side circuit open or Cruise system problem (speed error) or Manifold Absolute Pressure (MAP) sensor circuit out of range

Code 64

Oxygen Sensor (02S), right side - lean exhaust indicated

Code 65

Oxygen Sensor (02S), right side - rich exhaust indicated or Cruise servo position circuit or Fuel injector circuit low current

Code 66

A/C pressure sensor circuit fault, probably low pressure or Engine power switch, voltage high or low or PCM fault 5.7L (VIN J)

Code 67

A/C pressure sensor circuit, sensor or A/C clutch circuit failure or Cruise switch circuit fault

Code 68

A/C compressor relay (shorted circuit) or Cruise system fault

Code 69

A/C clutch circuit or head pressure high

Code 70

A/C refrigerant pressure sensor circuit (high pressure)

Code 71

A/C evaporator temperature sensor circuit (low temperature)

Code 72

Gear selector switch circuit

Code 73

A/C evaporator temperature sensor circuit (high temperature)

Code 75

Digital EGR #1 solenoid error

Code 76

Digital EGR #2 solenoid error

Code 77

Digital EGR #3 solenoid error

Code 79

Vehicle Speed Sensor (VSS) circuit signal high

Code 80

Vehicle Speed Sensor (VSS) circuit signal low

Code 81

Brake input circuit fault - Torque converter clutch signal

Code 82

Ignition Control (IC) 3X signal error

Code 85

PROM error

Code 86

Analog/Digital ECM error

Code 87

EEPROM error

Code 99

Power management

OBD-II DIAGONSTIC TROUBLE CODES (DTCS)



The following code list covers all 1994-96 vehicles, except for the 1994 5.7L (VIN J) engine. Some 1994-95 vehicles also utilize some OBD-I codes.

P0100

Mass or Volume Air Flow Circuit Malfunction

P0101

Mass or Volume Air Flow Circuit Range/Performance Problem

P0102

Mass or Volume Air Flow Circuit Low Input

P0103

Mass or Volume Air Flow Circuit High Input

P0104

Mass or Volume Air Flow Circuit Intermittent

P0105

Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction

P0106

Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

P0107

Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

P0108

Manifold Absolute Pressure/Barometric Pressure Circuit High Input

P0109

Manifold Absolute Pressure/Barometric Pressure Circuit Intermittent

P0110

Intake Air Temperature Circuit Malfunction

P0111

Intake Air Temperature Circuit Range/Performance Problem

P0112

Intake Air Temperature Circuit Low Input

P0113

Intake Air Temperature Circuit High Input

P0114

Intake Air Temperature Circuit Intermittent

P0115

Engine Coolant Temperature Circuit Malfunction

P0116

Engine Coolant Temperature Circuit Range/Performance Problem

P0117

Engine Coolant Temperature Circuit Low Input

P0118

Engine Coolant Temperature Circuit High Input

P0119

Engine Coolant Temperature Circuit Intermittent

P0120

Throttle/Pedal Position Sensor/Switch "A" Circuit Malfunction

P0121

Throttle/Pedal Position Sensor/Switch "A" Circuit Range/Performance Problem

P0122

Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input

P0123

Throttle/Pedal Position Sensor/Switch "A" Circuit High Input

P0124

Throttle/Pedal Position Sensor/Switch "A" Circuit Intermittent

P0125

Insufficient Coolant Temperature For Closed Loop Fuel Control

P0126

Insufficient Coolant Temperature For Stable Operation

P0130

O2 Circuit Malfunction (Bank no. 1 Sensor no. 1)

P0131

O2 Sensor Circuit Low Voltage (Bank no. 1 Sensor no. 1)

P0132

O2 Sensor Circuit High Voltage (Bank no. 1 Sensor no. 1)

P0133

O2 Sensor Circuit Slow Response (Bank no. 1 Sensor no. 1)

P0134

O2 Sensor Circuit No Activity Detected (Bank no. 1 Sensor no. 1)

P0135

O2 Sensor Heater Circuit Malfunction (Bank no. 1 Sensor no. 1)

P0136

O2 Sensor Circuit Malfunction (Bank no. 1 Sensor no. 2)

P0137

O2 Sensor Circuit Low Voltage (Bank no. 1 Sensor no. 2)

P0138

O2 Sensor Circuit High Voltage (Bank no. 1 Sensor no. 2)

P0139

O2 Sensor Circuit Slow Response (Bank no. 1 Sensor no. 2)

P0140

O2 Sensor Circuit No Activity Detected (Bank no. 1 Sensor no. 2)

P0141

O2 Sensor Heater Circuit Malfunction (Bank no. 1 Sensor no. 2)

P0142

O2 Sensor Circuit Malfunction (Bank no. 1 Sensor no. 3)

P0143

O2 Sensor Circuit Low Voltage (Bank no. 1 Sensor no. 3)

P0144

O2 Sensor Circuit High Voltage (Bank no. 1 Sensor no. 3)

P0145

O2 Sensor Circuit Slow Response (Bank no. 1 Sensor no. 3)

P0146

O2 Sensor Circuit No Activity Detected (Bank no. 1 Sensor no. 3)

P0147

O2 Sensor Heater Circuit Malfunction (Bank no. 1 Sensor no. 3)

P0150

O2 Sensor Circuit Malfunction (Bank no. 2 Sensor no. 1)

P0151

O2 Sensor Circuit Low Voltage (Bank no. 2 Sensor no. 1)

P0152

O2 Sensor Circuit High Voltage (Bank no. 2 Sensor no. 1)

P0153

O2 Sensor Circuit Slow Response (Bank no. 2 Sensor no. 1)

P0154

O2 Sensor Circuit No Activity Detected (Bank no. 2 Sensor no. 1)

P0155

O2 Sensor Heater Circuit Malfunction (Bank no. 2 Sensor no. 1)

P0156

O2 Sensor Circuit Malfunction (Bank no. 2 Sensor no. 2)

P0157

O2 Sensor Circuit Low Voltage (Bank no. 2 Sensor no. 2)

P0158

O2 Sensor Circuit High Voltage (Bank no. 2 Sensor no. 2)

P0159

O2 Sensor Circuit Slow Response (Bank no. 2 Sensor no. 2)

P0160

O2 Sensor Circuit No Activity Detected (Bank no. 2 Sensor no. 2)

P0161

O2 Sensor Heater Circuit Malfunction (Bank no. 2 Sensor no. 2)

P0162

O2 Sensor Circuit Malfunction (Bank no. 2 Sensor no. 3)

P0163

O2 Sensor Circuit Low Voltage (Bank no. 2 Sensor no. 3)

P0164

O2 Sensor Circuit High Voltage (Bank no. 2 Sensor no. 3)

P0165

O2 Sensor Circuit Slow Response (Bank no. 2 Sensor no. 3)

P0166

O2 Sensor Circuit No Activity Detected (Bank no. 2 Sensor no. 3)

P0167

O2 Sensor Heater Circuit Malfunction (Bank no. 2 Sensor no. 3)

P0170

Fuel Trim Malfunction (Bank no. 1)

P0171

System Too Lean (Bank no. 1)

P0172

System Too Rich (Bank no. 1)

P0173

Fuel Trim Malfunction (Bank no. 2)

P0174

System Too Lean (Bank no. 2)

P0175

System Too Rich (Bank no. 2)

P0176

Fuel Composition Sensor Circuit Malfunction

P0177

Fuel Composition Sensor Circuit Range/Performance

P0178

Fuel Composition Sensor Circuit Low Input

P0179

Fuel Composition Sensor Circuit High Input

P0180

Fuel Temperature Sensor "A" Circuit Malfunction

P0181

Fuel Temperature Sensor "A" Circuit Range/Performance

P0182

Fuel Temperature Sensor "A" Circuit Low Input

P0183

Fuel Temperature Sensor "A" Circuit High Input

P0184

Fuel Temperature Sensor "A" Circuit Intermittent

P0185

Fuel Temperature Sensor "B" Circuit Malfunction

P0186

Fuel Temperature Sensor "B" Circuit Range/Performance

P0187

Fuel Temperature Sensor "B" Circuit Low Input

P0188

Fuel Temperature Sensor "B" Circuit High Input

P0189

Fuel Temperature Sensor "B" Circuit Intermittent

P0190

Fuel Rail Pressure Sensor Circuit Malfunction

P0191

Fuel Rail Pressure Sensor Circuit Range/Performance

P0192

Fuel Rail Pressure Sensor Circuit Low Input

P0193

Fuel Rail Pressure Sensor Circuit High Input

P0194

Fuel Rail Pressure Sensor Circuit Intermittent

P0195

Engine Oil Temperature Sensor Malfunction

P0196

Engine Oil Temperature Sensor Range/Performance

P0197

Engine Oil Temperature Sensor Low

P0198

Engine Oil Temperature Sensor High

P0199

Engine Oil Temperature Sensor Intermittent

P0200

Injector Circuit Malfunction

P0300

Random/Multiple Cylinder Misfire Detected

P0323

Ignition/Distributor Engine Speed Input Circuit Intermittent

P0325

Knock Sensor no. 1-Circuit Malfunction (Bank no. 1 or Single Sensor)

P0327

Knock Sensor no. 1-Circuit Low Input (Bank no. 1 or Single Sensor)

P0332

Knock Sensor no. 2-Circuit Low Input (Bank no. 2)

P0335

Crankshaft Position Sensor "A" Circuit Malfunction

P0336

Crankshaft Position Sensor "A" Circuit Range/Performance

P0337

Crankshaft Position Sensor "A" Circuit Low Input

P0400

Exhaust Gas Recirculation Flow Malfunction

P0403

Exhaust Gas Recirculation Circuit Malfunction

P0410

Secondary Air Injection System Malfunction

P0412

Secondary Air Injection System Switching Valve "A" Circuit Malfunction

P0420

Catalyst System Efficiency Below Threshold (Bank no. 1)

P0430

Catalyst System Efficiency Below Threshold (Bank no. 2)

P0441

Evaporative Emission Control System Incorrect Purge Flow

P0443

Evaporative Emission Control System Purge Control Valve Circuit Malfunction

P0500

Vehicle Speed Sensor Malfunction

P0506

Idle Control System RPM Lower Than Expected

P0507

Idle Control System RPM Higher Than Expected

P0530

A/C Refrigerant Pressure Sensor Circuit Malfunction

P0531

A/C Refrigerant Pressure Sensor Circuit Range/Performance

P0562

System Voltage Low

P0563

System Voltage High

P0601

PCM Memory

P0602

PCM not programmed

P1107

MAP Sensor Voltage Intermittently Low

P1111

IAT Sensor Circuit Intermittent High Voltage

P1112

IAT Sensor Circuit Intermittent Low Voltage

P1114

ECT Sensor Circuit Intermittent Low Voltage

P1115

ECT Sensor Circuit Intermittent High Voltage

P1121

TP Sensor Voltage Intermittently High

P1122

TP Sensor Voltage Intermittently Low

P1133

HO 2 S Insufficient Switching Sensor

P1133

HO 2 S Insufficient Switching Bank #1, Sensor #1

P1134

HO 2 S #1 Transition Time Ratio

P1134

HO 2 S Transition Time Ratio Bank #1, Sensor #1

P1153

HO 2 S Insufficient Switching Sensor Bank #2, Sensor #1

P1154

HO 2 S Transition Time Ratio Bank #2, Sensor #1

P1345

Crankshaft/Camshaft (CKP/CMP) Correlation

P1350

Ignition Control (IC) Circuit Malfunction

P1351

Ignition Control (IC) Circuit High Voltage

P1361

Ignition Control (IC) Circuit Not Toggling

P1361

Ignition Control (IC) Circuit Low Voltage

P1380

Electronic Brake Control Module (EBCM) DTC Detected Rough Road Data Unusable

P1381

Misfire Detected, No EBCM/PCM/VCM Serial Data

P1406

EGR Pintle Position Circuit Fault

P1415

AIR System Bank #1

P1416

AIR System Bank #2

P1441

EVAP Control System Flow During Non-Purge

P1508

IAC System Low RPM

P1509

IAC System High RPM

P1520

PNP Circuit

P1530

Ignition Timing Adjustment Switch Circuit

P1600

PCM Battery Circuit Fault

P1635

5-Volt Reference "A" Circuit

P1639

5-Volt Reference "B" Circuit

P1641

MIL Control Circuit

P1651

Fan #1 Relay Control Circuit

P1652

Fan #2 Relay Control Circuit

P1654

A/C Relay Control

P1655

EVAP Purge Solenoid Control Circuit

P1672

Low Engine Oil Level Light Control Circuit

 
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