Diagnostic Circuit Check
NOTE:
DIAGNOSTIC CIRCUIT CHECK must be performed before any other testing. This test will determine if system is working properly.
- With ignition on and engine stopped, "Check Engine" light should be on. This is a bulb check.
- With ignition on and engine stopped, jumper between terminals A and C or ground terminal A of ALDL to activate trouble code system. See Fig 1 . The "Check Engine" light will begin to flash a trouble code 12.
- Code 12 consists of one flash, a short pause, then 2 flashes. There will be a longer pause and code 12 will repeat 2 more times. This check indicates that self-diagnostic system is working.
NOTE: Remove ground from test terminal before starting engine.
- With engine running, "Check Engine" light off. Ground test terminal A, check for trouble codes. If any codes exist, refer to TROUBLE CODE table.
TROUBLE CODES
| Trouble Code | Application |
|---|---|
| 12 | No Distributor Reference |
| 13 | Oxygen Sensor Circuit |
| 14 | Shorted Coolant Sensor Circuit |
| 15 | Open Coolant Sensor Circuit |
| 21 | Idle Switch Circuit |
| 22 | Open Fuel Cut-Off Relay Circuit |
| 23 | Open or Grounded Feedback Solenoid Circuit |
| 25 | Vacuum Switching Valve Circuit |
| 42 | High Voltage from Fuel Cut Relay |
| 44 | Lean Oxygen Sensor Condition |
| 45 | Rich Oxygen Sensor Condition |
| 51 | Faulty Calibration Unit (PROM) |
| 53 | High Voltage from Vacuum Switching Valve |
| 54 | High Voltage from Feedback Solenoid |
| 55 | Faulty ECM or O2 Sensor |