Connect white (test lead) and black (ground lead) wires that are branched from harness approximately eight inches from ECM. After leads are grounded, the "Check Engine" light will flash the diagnostic trouble codes. The DTC's are indicated by the flashing CEL.
FLASH, FLASH, pause, FLASH, FLASH, FLASH = Code 23.
If only one diagnostic trouble code is stored, the DTC will repeat continuously until test leads are disconnected. If more than one diagnostic trouble code is stored, each DTC will repeat three times, starting with the lowest, then proceed to the next DTC. After all DTC's have been displayed, the pattern will repeat.I-MARK 84-85
Connect male and female test leads taped into wire harness near ECM. After leads are connected, the "Check Engine" lamp will flash the trouble codes. The DTC's are indicated by the flashing CEL.
FLASH, FLASH, pause, FLASH, FLASH, FLASH = Code 23.
If only one diagnostic trouble code is stored, the DTC will repeat continuously until test leads are disconnected. If more than one diagnostic trouble code is stored, each DTC will repeat three times, starting with the lowest, then proceed to the next DTC. After all DTC's have been displayed, the pattern will repeat.
86-87 Impulse located near the ECM connector, is used to actuate the Engine Control Module (ECM) trouble code memory within the module. Two terminals (A and C) of this connector are used to activate the diagnostic trouble code system in the ECM. With the ignition switch turned On, engine Off, connect a jumper wire between terminals A and C. The "Check Engine" lamp will begin by flashing a DTC 12. DTC 12 = flash, pause, flash, flash. There will be a longer pause and a code 12 will repeat two more times. This code indicates the self-diagnostic system is operating. The cycle will then repeat until the engine is started or the ignition is switched Off. In most cases, DTC's will be checked with the engine running since no DTC's other than DTC 12 or 51 will be present without the engine running. Remove jumper wire from ALDL connector before starting engine. Reconnect jumper wire after engine is running.
Throttle Body Fuel Injection
The ECM test connection is located under the center console.
A built-in, self diagnostic system will identify problems in the throttle body fuel injection system. When a problem is detected, the diagnostic system will illuminate the "Check Engine" light.
When the engine is started, the Check Engine light should turn off.. If the light remains lit, the self diagnostic has detected a problem. To determine where the problem exists, ground the "Test" terminal of the connector with the ignition On, engine Off and watch the check engine light. Each DTC will flash three times (lowest to highest).
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