Reading Diagnostic Trouble Codes

The power loss/check engine lamp on the instrument panel will illuminate if the logic module or SMEC receives an incorrect signal or no signal from the coolant temperature sensor, charge temperature sensor, MAP sensor, throttle position sensor or battery voltage sensor input depending on vehicle application. This lamp indicates that the logic module or SMEC has gone into the ``limp in mode'' to keep the system operational, and indicates an immediate need for service.

The power loss/check engine lamp will also light for several seconds each time the ignition key is turned on as a bulb check.
If suitable diagnostic read-out tool is not available, stored fault codes can be accessed directly through the power loss/check engine lamp. To call up codes, cycle ignition switch on, off, on, off and on within 5 seconds. Stored codes will be indicated by flashes of the power loss/check engine lamp. The codes will be indicated as two digit numbers, with a four second pause between codes.

An example of a code is as follows:
1. Power Loss/Check Engine Lamp illuminated for approximately 2 to 3 seconds as a bulb check, then turns off.
2. Lamp flashes two times, pauses, then flashes six times.
3. Lamp pauses for approximately four seconds.
4. Lamp flashes three times, pauses, then flashes one time.
5. This would indicate that code 26 and 31 are stored. The lamp will continue to flash until all stored codes have been displayed.
Once the lamp starts flashing the stored fault codes, it cannot be stopped. If a code is missed, the entire procedure must be repeated. The lamp will not indicate if oxygen feedback system is switching lean-rich or if idle motor system is operational. The lamp also cannot be used to perform actuation test mode, sensor test mode or engine running test mode.