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Trouble Code Table
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#
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Curcuit or Systam
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Probable Cause
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12
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No reference pulse to ECM
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This code should flash whenever the Test terminal is grounded with the ignition ON and the engine not running. If additional Trouble Codes are stored (indicating a problem), they will appear after this code has flashed three times. With the engine running, the appearance of this code indicated that no references from the distributor are reaching the ECM. Carefully check the four-terminal EST connector at the distributor.
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13
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Oxygen Sensor Circuit
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Check the wiring and connector from the oxygen sensor, replace oxygen sensor
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14
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Coolent Sensor Circuit
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If the engine is experiencing overheating problems, the problem must be rectified before continuing. Check all wiring and connectors associated with the sensor, replace the coolent sensor
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15
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Coolent Sensor Circuit (low temperature indicated)
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See above, also check the thermostat for proper operation
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19
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Crankshaft Position Sensor reference signal intermittent
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The reference signal from the crankshaft sensor is intermittent. Inspect PCM harness connector and crankshaft sensor wire harness for shorts of a damaged harness
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21
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TPS circuit (signal voltage high
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Check for sticking of misadjusted TPS. Check all wiring and connections at the TPS and at the ECM. Adjust or replace TPS.
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22
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TPS circuit (signal voltage low)
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See Above
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23
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Mixture Control (M/C) solenoid circuit (carbureted models only)
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Check electrical connections at the M/C solenoid. If OK, clear the ECM memory and recheck for code(s) after driving the vehicle Check wiring connections at the ECM. Check wiring from M/C solenoid
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23
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Manifold Air Temperature(MAT) - (1986-1990 models)
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Check MAT sensor, wiring and all connections for an open. Replace the MAT sensor
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23
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Intake Air Temperature (IAT) sonsor circuit (low temperature)
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See above
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24
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Vehicle Speed sensor (VSS) circuit
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Fault in this circuit should be indicated only while the vehicle is in motion. Disregard code 24 if set when drive wheels are not turning. Check connections at the ECM. Check the TPS setting.
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25
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Manifold Air Temperature (MAT) sensor circuit (low temperature) - 1990 and earlier
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Check the resistance of the MAT sensor. Check the wiring and connectors to the sensor. Replace the MAT sensor
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25
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Intake Air Temperature (IAT) sensor circuit (high temperature) - 1992 and later
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Check the resistance of the IAT sensor. Check the wiring and connectors to the sensor. Replace the IAT sensor
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26
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Quad-Driver Module (QDM) circuit - 1994 2.2L
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QDMs are switches within the PCM used to control various components such as; canister purge solenoid, EGR solenoid, cooling fan relay, etc. Due to the complexity of the system, it is suggested that diagnosis and repair of QDM malfunctions be left to a dealer service department or other authorized repair facility
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27/28
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QDM circuits - 1994 2.2L
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See above
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31
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Wastegate actuator - (turbo models only)
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Possible sticking wastegate actuator or wastegate. Also check power to the ignition and/or a faulty ECM
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32
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No altitude compensator voltage - (carbureted models only)
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Check connections at altitude compensator. Check for an open circuit in the wiring from the sensor to the ECM. Replace the altitude compensator
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32
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Exhaust Gas Recirculation (EGR) failure
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Check the vacuum source and all vacuum lines. Check the EGR valve or ECM as necessary
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33
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Manifold Absolute Pressure (MAP) sensor or circuit
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Check vacuum hose(s) from MAP sensor. Check electrical connections at the ECM. Replace MAP sensor
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33
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MAF sensor or circuit
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Excessive airflow indicated. Check thermal C on the MAF sensor; it should be about 0.5 volts at idle and 4.7 volts at wide open throttle. Trace the wire form terminal C and look for and open circuit condition. Replace the MAF sensor.
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34
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Vacuum sensor circuit - (carbureted models only)
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Check the wiring leading to terminals 20, 21 and 22 of the ECM. Check the connections at the ECM. Check the vacuum sensor wiring and connections. Replace the vacuum sensor.
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34
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Mass Air Flow (MAF) sensor or circuit
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Low airflow indicated. Check thermal C on the MAF sensor; it should be about 0.5 volts at idle and 4.7 volts at wide open throttle. Trace the wire form terminal C and look for and open circuit condition. Replace the MAF sensor.
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34
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Manifold Absolute Pressure (MAP) sensor or circuit
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Check for an open or shorted to ground circuit. Check the MAP sensor. Replace it if malfunctioning
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35
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Idle speed control Circuit (IAC valve)
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Idle RPM too low or too high. Check minimum idle speed, check fuel pressure, and check for leaking injector and obstructions in the throttle body. Replace the IAC valve.
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41
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No distributor reference signal to the ECM at specified vacuum - (carbureted models only)
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Check all wires and connections at the distributor. Check distributor pick-up coil connections. Check vacuum sensor circuit
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41
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Cylinder select error
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Remove the access cover on the ECM and check to see that eh MEM_CAL, PROM or CALPAK is installed properly. Clear the trouble code and see if the code resets. If so, replace the MEM_CAL, PROM or CALPAK
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42
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Electronic Spark Timing (EST) circuit
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Check the wiring and connectors between the ignition module and the ECM. Replace the ignition module. Replace the ECM
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43
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Electronic Spark Control (ECS) circuit or Knock sensor (KS) circuit
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Check wiring and connectors form the knock sensor to the ESC controller or ECM for an open or short to ground; if necessary, reroute the harness away from other wires suck as spark plugs, etc. Replace the knock sensor
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44
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Lean exhaust
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Check the wiring and connectors form the oxygen sensor to the ECM. Check the ECM ground terminal. Check for a sticking M/C solenoid. Check the fuel pressure. Check for vacuum leaks at the carburetor base gasket; throttle body gasket, vacuum hoses or intake manifold gasket. Replace the oxygen sensor
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45
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Rich exhaust
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Check for a sticking M/C solenoid. Check wiring at M/C solenoid connector. Check the evaporative charcoal canister and its components for the presence of fuel. Check for fuel contaminated oil. Check the fuel pressure regulator. Check for a leaking fuel injector. Check for a sticking EGR valve. Replace the oxygen sensor
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51
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PROM/EPROM error
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Faulty or incorrect PROM/EEPROM. Diagnosis should be performed by a dealer service department or other repair shop
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52
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CAL-PAK error
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Faulty or incorrect CAL-PAK. Diagnosis should be performed by a dealer service department or other repair shop
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53
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System over voltage
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Code 53 will set if the voltage at the ECM is greater than 17.1 volts or less than 10 volts. Check the charging system
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54
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Mixture control (M/C) solenoid - (carbureted models only)
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Check all M/C solenoid and ECM wires and connections. Replace the M/C solenoid
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54
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Fuel pump circuit
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Check the fuel pump relay, circuit and connections. Check the oil pressure switch. Repair/replace faulty components
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55
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ECM/PCM
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Be sure the ECM/PCM ground connections are tight. If they are, replace the ECM/PCM
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61
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Contaminated oxygen sensor
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Replace the oxygen sensor. A contaminated sensor can be caused by fuel additives containing silicon or non-GM approved sealant or lubricants
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62
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Transaxle gear switch signal circuit
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Check for an open circuit with a voltmeter ant he TCC connector. Voltage should be about 12 volts. Further diagnosis is best left to a dealer with the proper diagnostic tools
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63
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Manifold Absolute Pressure (MAP) sensor circuit (low vacuum detected)
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Check wiring and connections from the MAP sensor the ECM. Check the vacuum hoses to the sensor for leaks. Replace the MAP sensor. Replace the ECM
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64
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Manifold Absolute Pressure (MAP) sensor circuit (high vacuum detected)
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Check the wiring and connections from the MAP sensor the ECM. Replace the MAP sensor, Replace the ECM
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66
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A/C refrigerant pressure sensor circuit
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Check the sensor electrical terminal connections and for a possible short to ground or open circuit in the sensor wiring. Replace the A/C refrigerant pressure sensor
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