62 lines
3.3 KiB
Plaintext
62 lines
3.3 KiB
Plaintext
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CODES USED BY COMPUTERS IN GM CARS
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New cars use computers to store and remember malfunctions that occur.
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These are displayed in the flashing sequences in the instrument cluster. A
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typical sequence of instructions follows:
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Locate the C3 diagnostic connector (also called the "ALCL"). It is usually
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under the dash on the drivers side. On the Ponitac Fiero, however, it is
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located in the console between the seats. Short the 'A' & 'B' positions of
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the diagnostic conector ('B' is ground), then turn the ignition key on but do
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not start the engine.
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CHECK ENGINE OR SERVICE ENGINE SOON light on dash will flash out the
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number 12 ( flash - pause - flash flash ) which means the self diagnostic
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mode is working. This will be repeated 3 times. Any trouble codes the
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computer (called the Electronic Control Module or ECM) has stored will then
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be flashed out ( for example: code 23 is ( flash flash - pause - flash flash
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flash ). If more then one code has been stored, they will be flashed out in
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order, each repeated 3 times. Look up the code in the following chart to
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find the faulty circuit or component.
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NOTE: Do not automatically replace a component without first checking its
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wiring and connectors. Also, it is good practice to test the component
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further using a digital volt/ohm meter as described in the vehicle's service
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manual. Remove the A to B short and turn off the ignition. After the
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repairs, clear the trouble codes from the computor's memory by disconnecting
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the fuse marked 'ECM' for at least 10 seconds.
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C3 TROUBLE CODES
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12- Normal code with ignition on and engine off. Indicates
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no distributor reference pulse to ECM. Not stored in
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memory.
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13- Oxygen sensor or it circuit
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14- Coolant Temperature Sensor circuit shorted.
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15- Coolant Temperature Sensor circuit open.
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21- Throttle Position Sensor (TPS) or its circuit.
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22- Throttle Position Sensor circuit voltage low due
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to grounded circuit or faulty adjustment of TPS.
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23- Mixture Control (MC) Solenoid circuit open or
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grounded.
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24- Vehicle Speed Sensor (VSS) or its circuit
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32- Baromteric Pressure Sensor circuit voltage low.
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34- Vacuum Sensor or Manifold Absolute Pressure (MAP) circuit.
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35- Idle Speed Control (SC) Switch circuit shorted.
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41- No distributor reference pulse to the ECM. Unlike code 12,
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this will be stored in the ECM.
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42- Electronic Spark Timing (EST) bypass circuit, or EST
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circuit open or grounded.
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43- Electronic Spark Control retard signal for too long
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a time.
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44- Lean exhaust
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45- Rich exhaust
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51- Prom (programmed read only memory) calibration unit faulty
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or improperly installed in ECM.
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53- Exhaust Gas Recirculation (EGR) valve vacuum sensor
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has received improper vacuum signal.
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54- Shorted Mixture Control Solenoid circuit and/or
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faulty ECM.
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55- Grounded Vref (terminal 21), high Oxygen Sensor circuit
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sensor voltage, or faulty ECM.
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