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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - Tests W/Codes - 5.2L CNG) >> Self-Diagnostic Tests >> Test TC-26A - Auto Shutdown Relay Control Circuit (DTC 42)

Test TC-26A - Auto Shutdown Relay Control Circuit (DTC 42)

WARNING: This page is about a different car, the 1995 Dodge Ram Wagon, 1995 Dodge Ram Van, 1995 Dodge Pickup, and 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using scan tool, erase DTCs and actuate Auto Shutdown (ASD) relay. If ASD relay does not click, go to step 4). If ASD relay clicks, condition required to set DTC is not present at this time. AUTO SHUTDOWN RELAY CONTROL CIRCUIT DTC sets if ASD and high pressure fuel solenoid relay control circuit is not in proper state when checked by Powertrain Control Module (PCM) during cranking.
  2. Possible causes are open or short in ASD relay and high pressure fuel solenoid relay control circuit, open or short in ASD relay control circuit (Dark Blue/Yellow wire), open or short in ignition 12-volt feed circuit (Red wire on AB body; Red/White wire on AN and BR bodies), and failed control circuit driver in PCM.
  3. Inspect all related wiring and connectors. Repair as necessary. Perform TEST VER-2. If wiring and connectors are okay, wiggle wiring harness from ASD relay to PCM. Ensure actuator test is still running and try to reset DTC. Using scan tool, read DTCs. If AUTO SHUTDOWN RELAY CONTROL CIRCUIT DTC returns, repair wiring harness where wiggling caused problem to occur. Perform TEST VER-2. If AUTO SHUTDOWN RELAY CONTROL CIRCUIT DTC does not return, test is complete. Perform TEST VER-2.
  4. Disconnect and inspect ASD relay connector. Repair as necessary. Using scan tool in voltmeter mode, check voltage on ASD relay connector, ignition 12-volt feed circuit (Red wire on AB body; Red/White wire on AN and BR bodies). If voltage is less than 10 volts, repair open in Red wire, Red/White wire or Dark Blue/White wire. Perform TEST VER-2.
  5. If voltage is more than 10 volts, turn ignition off. Disconnect and inspect Powertrain Control Module (PCM) connector for damaged, pushed-out or miswired terminals. Repair as necessary. Perform TEST VER-2.
  6. If connector is okay, put scan tool in ohmmeter mode. Using scan tool, check resistance of ASD relay connector, ASD relay control circuit (Dark Blue/Yellow wire). If resistance is less than 5 ohms, repair short to ground in Dark Blue/Yellow wire. Perform TEST VER-2.
  7. If resistance is more than 5 ohms, use an external ohmmeter to check resistance of ASD relay control circuit (Dark Blue/Yellow wire) between PCM connector terminal No. 51 and ASD relay connector. If resistance is more than 5 ohms, repair open in Dark Blue/Yellow wire. Perform TEST VER-2. If resistance is less than 5 ohms, replace PCM. Perform TEST VER-2.
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