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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Engine Controls - Tests W/Codes - 8.0L) >> Self-Diagnostic Tests >> Test TC-25A - Ignition Coil #3 Primary Circuit (DTC 43)

Test TC-25A - Ignition Coil #3 Primary Circuit (DTC 43)

WARNING: This page is about a different car, the 1995 Dodge Pickup and 1995 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION  . For wiring diagrams, see WIRING DIAGRAMS  section at the end of this article.
  1. Using scan tool, erase trouble codes. Turn ignition off. Disconnect spark plug cable at No. 8 spark plug. Insert an insulated screwdriver in spark plug cable terminal. Hold screwdriver within 1/4" of ground.
    NOTE: When checking for spark, consider one or two sparks as a no -spark condition.
  2. Turn ignition on with engine off. Using scan tool, actuate ignition coil No. 3, while watching for spark. If good spark does not occur, go to step 6). If good spark occurs, condition required to set code is not present at this time. Go to next step.
  3. IGNITION COIL #3 PRIMARY CIRCUIT trouble code sets when Powertrain Control Module (PCM) does not see peak current reached. Possible causes are: open ignition coil No. 3 primary circuit, open or shorted driver circuit (Red/Yellow wire), open Auto Shutdown (ASD) output circuit (Dark Green/Orange wire) or failed PCM.
  4. Inspect all related wiring and connectors and repair as necessary. Perform TEST VER-2. If no problems are found in wiring and connectors, go to next step.
  5. Start engine. Wiggle wiring harness from front coil pack to PCM. If spark becomes erratic or stops, repair harness where wiggling causes problem to occur. Perform TEST VER-2. If spark does not become erratic or stop, see INACTIVE DTC CONDITION  . Perform TEST VER-2.
  6. Turn ignition off. Disconnect rear ignition coil connector. Inspect rear ignition coil connector for damaged, pushed-out or miswired terminals. Repair rear ignition coil connector as necessary. Perform TEST VER-2.
  7. If rear ignition coil connector is okay, turn ignition on. Using scan tool, actuate ignition coil No. 3. Using scan tool in voltmeter mode, check voltage on rear ignition coil connector, Auto Shutdown (ASD) output circuit (Dark Green/Orange wire). If voltage is less than 10 volts, repair open Dark Green/Orange wire. Perform TEST VER-2.
  8. If voltage is more than 10 volts, turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Using scan tool in ohmmeter mode, check resistance of rear ignition coil connector, ignition coil No. 3 driver circuit (Red/Yellow wire). If resistance is less than 5 ohms, repair short to ground in Red/Yellow wire. Perform TEST VER-2.
  9. If resistance is more than 5 ohms, connect a jumper wire between rear ignition coil connector, ignition coil No. 3 driver circuit (Red/Yellow wire) and engine ground. Check resistance of Red/Yellow wire. If resistance is more than 5 ohms, repair open Red/Yellow wire. Perform TEST VER-2. If resistance is less than 5 ohms, go to next step.
  10. Using an external ohmmeter, check resistance of ignition coil No. 3 primary circuit. Put one ohmmeter lead on rear ignition coil, cylinders No. 8 and 9 terminal. Put other ohmmeter lead on rear ignition coil ASD relay output terminal. See Figure . If resistance is more than 2 ohms, replace rear ignition coil. Perform TEST VER-2. If resistance is less than 2 ohms, replace PCM. Perform TEST VER-2.
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