- Description of On-Board Diagnostics

DIAGNOSTIC MODES
The Engine Control Module (ECM) has two different diagnostic modes: normal and test.

Normal Mode
When "TE1" is grounded, the ECM enters its normal diagnostic mode and flashes Diagnostic Trouble Codes (DTCs), through the Malfunction Indicator Lamp (MIL), that have been detected one time within the last two ignition cycles.

Test Mode
When "TE2" is grounded, the ECM enters its test diagnostic mode and lowers the threshold at which DTCs can be stored in the ECM's memory. This function is helpful when diagnosing intermittent problems. With "TE1" and "TE2" grounded, DTCs that cannot be read in the normal diagnostic mode can be read.