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Home >> Isuzu >> 2007 >> i-290 LS, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 13 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> DTC B0248, B0268, B0408, B0413, B0418, B0423, B0428, B0433, B3531, B3761, B3773, or B3782 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
  2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal 2 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.
    • If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
  4. Verify the appropriate scan tool parameter is less than 3 counts.
    • If greater than the specified range, test the signal circuit terminal 3 for a short to ground. If the circuit tests normal, replace the HVAC control module.
  5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 2. Verify the appropriate scan tool actuator parameter is greater than 250 counts.
    • If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  6. Reconnect the harness connector at the appropriate actuator.
  7. Disconnect the HVAC control module.
    8. IMPORTANT: Apply power and ground to the actuator for no more than 2 seconds at a time or the actuator could be damaged.
    IMPORTANT: When performing the following tests, make sure that the device is not already at its end of travel position by switching the polarity applied to the actuator twice if the actuator did not move in one direction.
  8. Install a 20 amp fused jumper wire between the appropriate control circuit terminal and 12 volts. Momentarily install a jumper wire between the appropriate control circuit terminal and ground. The actuator should move.
    • If the actuator does not move in both directions, test the control circuits for a short to voltage, short to ground or an open/high resistance. If the circuits test normal, test or replace the inoperative actuator.
  9. If all circuits test normal, replace the HVAC control module.
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