Electronic Control System: Testing
NOTE:
Before starting testing, ensure engine is in good mechanical condition and adjusted to specifications.
On all models, an LED is located on ECU under driver's side seat for self-diagnostic codes. LED is used to read codes set due to component failure. See appropriate LED CODES table in this article. To obtain codes, turn ignition switch to the "ON" position and count flashes of LED on ECU.
NOTE:
If unlisted codes are flashed by ECU LED, clear codes and recheck. If code still appears, substitute a known good ECU. If condition is rectified, replace original ECU.
On all models, System Checker Harness (07999-PD60000A ) is needed to test components. See Fig 1 . An Inspection Harness (07GMJ ML80100 ) is needed for testing specific 3-wire sensors. Both of these devices function as breakout boxes to access pin voltage signals while component is either in or out of circuit.
To reset ECU, remove No. 11 fuse in the under-hood relay box for 10 seconds to reset ECU.
LED CODE
| LED Blinks (1) | System Code | ||
|---|---|---|---|
| 0 | ECU | ||
| 1 | Oxygen Sensor A | ||
| 2 | Oxygen Sensor B | ||
| 3 | MAP Sensor | ||
| 5 | MAP Sensor | ||
| 6 | Coolant Temperature | ||
| 7 | Throttle Angle Sensor | ||
| 8 | TDC Sensor | ||
| 9 | No. 1 CYL Sensor | ||
| 10 | Intake Air Temperature Sensor | ||
| 12 | EGR System | ||
| 13 | Atmospheric Pressure Sensor | ||
| 14 | Electronic Air Control Valve | ||
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