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Tahoe / Yukon Service Manual

DTC B1038

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptors DTC B1038 Left Front Door Open Switch Signal Symptom Byte Information: Symptom Byte List Diagnostic Fault Information

Circuit number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
126 Signal B1038 11 B1038 15 B1038 15 B1038 29, B1038 64
1150 Ground — 1 — —
1. Door ajar indicator not displayed when driver door is open

Circuit/System Description The door open switch and the door ajar switch contacts will be open when the door is fully closed, the door switches within the door latch are designed so that the when the door is ajar, the contact in the door ajar switch closes, the voltage is pulled low and the window motor will then send a serial data message to the body control module indicating that the door is ajar. When the door is opened further, the contact in the door open switch will then decrease the resistance in the signal circuit to the ground for the door open signal circuit, the body control module will then determine from the change in the voltage level that the door is open. The K9 Body Control Module supplies the A23D Front Side Door Latch-Driver a 5V Reference through the open switch signal circuit 126. The A23D Front Side Door Latch-Driver contains a multiplexed resistor. When the driver door is closed the open switch contacts will be open, when the door is open the contacts in the switch will close which will decrease the resistance between signal circuit 126 and ground. The body control module will then determine from the change in the voltage level that the door is open. The M74D Front Side Door Window Regulator Motor-Driver provides the A23D Front Side Door Latch-Driver 12V through the door ajar signal circuit 745. Ground is applied at all times to the A23D Front Side Door Latch-Driver. When the driver door is closed the ajar switch contacts will be open, when the driver door is ajar the contacts in the switch will close providing ground to signal circuit 745. M74D Front Side Door Window Regulator Motor-Driver will then send a serial data message to the body control module indicating that the door is ajar. Conditions for Running the DTC Battery voltage is between 9–16 V. Conditions for Setting the DTC B1038 11 Circuit 126= Short to Ground— For greater than 60 s . B1038 15 Circuit 126= Open/High Resistance or Short to Voltage— For greater than 60 s B1038 29 Circuit 126= Signal circuit voltage is not within the expected high and low voltage values— For greater than 60 s B1038 64 Circuit 126= Active— For greater than 60 s Circuit 745= Inactive— For greater than 60 s Action Taken When the DTC Sets The driver information center will display the message: Service Steering Column Lock and Service Door Latch System. Conditions for Clearing the DTC The DTC will be current for as long as the fault is present. When the BCM receives a serial data message from the driver window motor that the door is ajar before the body control module detects the door open switch is active, then the DTC will be a history DTC. A history DTC will clear after 40 ignition cycles. Reference Information Schematic Reference Door Lock/Indicator Schematics Connector End View Reference Master Electrical Component List Description and Operation Door Ajar Indicator Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON.
  2. Verify the scan tool Left Front Door Ajar Switch parameter changes between Ajar and Closed when opening and closing the driver door. ⇒ If the parameter does not change Refer to Door Ajar Indicator Malfunction ⇓ If the parameter changes
  3. Verify the scan tool Driver Door Open Switch parameter changes between Open and Closed when opening and closing the driver door. ⇒ If the parameter does not change Refer to Circuit/System Testing ⇓ If the parameter changes
  4. A fault is not currently present and may be an intermittent condition Circuit/System Testing
  5. Ignition OFF, disconnect the harness connector at the A23D Front Side Door Latch-Driver. Ignition ON
  6. Test for greater than 4 V between the signal circuit terminal 2 and ground ⇒ If 4 V or less 2.1. Test circuit 126 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 2.2. Test circuit 126 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 2.3. Replace the K9 Body Control Module. ⇓ If greater than 4 V
  7. Test or replace the A23D Front Side Door Latch-Driver. Component Testing Static Test
  8. Ignition OFF, disconnect the harness connector at the A23D Front Side Door Latch-Driver.
  9. With the door unlatched, test for 725 Ω to 740 Ω between the signal terminal 2 and ground terminal 3 ⇒ If not within the specified range, replace the A23D Front Side Door Latch-Driver.
  10. With the door latched, test for 1450 Ω to 1480 Ω between the signal terminal 2 and ground terminal 3 ⇒ If not within the specified range, replace the A23D Door Latch Assembly-Driver. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Front Side Door Latch Replacement Control Module References for body control module replacement, setup, and programming