GM Metro/Sprint 1985-1993 Repair Guide

Diagnostic Trouble Codes-EFI System

Print

READING CODES



See Figure 1

Once the integrity of the system is confirmed, enter the Diagnostic Mode and read any stored codes. Once the Diagnostic Mode is engaged, the dash warning lamp should begin to flash.

The Metro uses Code 12 to indicate that no other codes are stored. If a fault is in memory, it will be broadcast as soon as the system enters Diagnostic Mode. The codes are stored and transmitted in numeric order from lowest to highest; each fault code is transmitted 3 times before moving to the next.

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

Record each code transmitted for later reference. Once all codes have been sent, the memory may need to be cleared during diagnostics. If there are no codes stored, but a driveability or emissions problem is evident, refer A-Charts.

To retrieve codes from the ECM without the use of a scan tool:

  1. Locate the diagnostic terminals at the bottom of the under dash fuse block.
  2.  
  3. Turn the ignition switch ON but do not start the engine.
  4.  
  5. Insert a spare fuse into the diagnostic terminals. This completes the ground circuit for the ECM diagnostic circuit. The CHECK ENGINE light should display Code 12 and/or any stored codes.
    1. An alternate diagnostic position is provided under the hood. The diagnostic connector is located next to the ignition coil.
    2.  
    3. Use a jumper to connect the diagnostic switch terminal to the ground terminal.
    4.  

  6.  
  7. Read the flashes of the CHECK ENGINE light to determine the codes. If the light flashes a Code 12, the system is functioning normally.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: 1989-91 EFI diagnostic code table

CIRCUIT/COMPONENT DIAGNOSIS AND REPAIR



Using the appropriate chart(s) based on the Diagnostic Circuit Check, the fault codes and scan tool data will lead to diagnosis and checking of a particular circuit or component. It is important to note that the fault code indicates a fault or loss of signal in an ECM-controlled system, not necessarily in the specific component. Detailed procedures to isolate the problem are included in each code chart; these procedures must be followed accurately to insure timely and correct repair. Following the procedure will also insure that only truly faulty components are replaced.

CLEARING CODES



Stored fault codes may be erased from memory at any time by removing power from the ECM for at least 30 seconds. This time period must be increased as the temperature drops. It may be necessary to clear stored codes during diagnosis to check for any recurrence during a test drive, but the stored codes must be written down when retrieved. The codes may still be required for subsequent troubleshooting. Whenever a repair is complete, the stored codes must be erased and the vehicle test driven to confirm correct operation and repair.

The ignition switch must be OFF any time power is disconnected or restored to the ECM. Severe damage may result if this precaution is not observed.

Removing the TAIL LAMP fuse from the under dash fuse box will interrupt power to the ECM without blanking other memories within the vehicle. The pink, 30 amp main fuse may be removed from the underhood fuse holder on the right front fender apron, but this will also disconnect power to the clock and the radio.

COMPONENT TESTING



See Figure 2



Click image to see an enlarged view

Fig. Fig. 2: 1989-91 EFI COMPONENT LOCATIONS

Oxygen Sensor
  1. Warm the engine to normal operating temperature.
  2.  
  3. Disconnect the connector of the oxygen sensor.
  4.  
  5. Connect a voltmeter between the sensor side terminal and ground.
  6.  

Never apply voltage to the oxygen sensor as it may cause damage to the sensor.

  1. With the engine running at 1200 rpm, check that the voltage from oxygen sensor varies between 0-0.9 volts.
  2.  
  3. After checking, reconnect oxygen sensor connector.
  4.  

Coolant Temperature Sensor
  1. Disconnect electrical connector from coolant temperature sensor.
  2.  
  3. Using an ohmmeter, check resistance between the sensor terminals.
  4.  
  5. With engine cold, resistance should be approximately 4000 ohms.
  6.  
  7. With engine at normal operating temperature, resistance should be less than 450 ohms.
  8.  

Throttle Switch
MANUAL TRANSMISSION
  1. Turn the ignition switch ON .
  2.  
  3. Backprobe the throttle switch connector LT GRN/WHT wire.
  4.  
  5. Voltage should be 4 volts.
  6.  
  7. Turn the ignition switch OFF and disconnect the throttle switch.
  8.  
  9. Turn the ignition switch ON and measure the voltage at the LT GRN/WHT wire terminal at the throttle switch connector.
  10.  
  11. Voltage should be 4 volts.
  12.  
  13. If switch is within specifications, check switch adjustment.
  14.  

Throttle Position Sensor
  1. Using a digital voltmeter, backprobe the throttle position sensor LT GRN/YEL wire.
  2.  
  3. Voltage should vary between 0.49-0.59 volts at closed throttle and 4.5-5.5 volts at wide open throttle.
  4.  
  5. If sensor is not within specifications, check for faulty connections or shorts.
  6.  

Manifold Air Temperature Sensor
  1. Disconnect the sensor electrical connector.
  2.  
  3. Measure the resistant between the connector terminals.
  4.  
  5. Resistance should be approximately 3400 ohms when the air temperature is 70°F (20°C).
  6.  
  7. If resistance is not within specification, check for faulty connections or shorts.
  8.  

Crankshaft Angle Sensor
  1. Disconnect the sensor electrical connector.
  2.  
  3. Check resistance between the sensor terminals.
  4.  
  5. Resistance should be 140-180 ohms.
  6.  
  7. If resistance is not within specification, check sensor air gap.
  8.  

See Figures 3 through 107



Click image to see an enlarged view

Fig. Fig. 3: 1989-91 ECM wiring diagram - conventional ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 4: 1989-91 ECM wiring diagram - conventional ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 5: 1989-91 ECM wiring diagram - conventional ignition with automatic transmission



Click image to see an enlarged view

Fig. Fig. 6: 1989-91 ECM wiring diagram - conventional ignition with automatic transmission



Click image to see an enlarged view

Fig. Fig. 7: 1989-91 ECM wiring diagram - ESA ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 8: 1989-91 ECM wiring diagram - ESA ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 9: 1989-91 EFI control module terminal identification - conventional ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 10: 1989-91 EFI control module terminal identification - conventional ignition with automatic transmission



Click image to see an enlarged view

Fig. Fig. 11: 1989-91 EFI control module terminal identification - ESA ignition with manual transmission



Click image to see an enlarged view

Fig. Fig. 12: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 13: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 14: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 15: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 16: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 17: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 18: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 19: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 20: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 21: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 22: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 23: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 24: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 25: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 26: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 27: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 28: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 29: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 30: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 31: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 32: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 33: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 34: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 35: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 36: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 37: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 38: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 39: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 40: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 41: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 42: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 43: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 44: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 45: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 46: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 47: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 48: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 49: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 50: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 51: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 52: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 53: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 54: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 55: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 56: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 57: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 58: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 59: 1992-93 EFI component locations



Click image to see an enlarged view

Fig. Fig. 60: 1992-93 ECM wiring diagram



Click image to see an enlarged view

Fig. Fig. 61: 1992-93 ECM wiring diagram



Click image to see an enlarged view

Fig. Fig. 62: 1992-93 ECM terminal identification



Click image to see an enlarged view

Fig. Fig. 63: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 64: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 65: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 66: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 67: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 68: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 69: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 70: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 71: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 72: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 73: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 74: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 75: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 76: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 77: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 78: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 79: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 80: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 81: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 82: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 83: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 84: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 85: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 86: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 87: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 88: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 89: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 90: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 91: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 92: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 93: 1989-91 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 94: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 95: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 96: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 97: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 98: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 99: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 100: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 101: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 102: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 103: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 104: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 105: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 106: 1992-93 EFI diagnostic chart



Click image to see an enlarged view

Fig. Fig. 107: 1992-93 EFI diagnostic chart

 
label.common.footer.alt.autozoneLogo