Subject: | Ignition Switch Diagnostic Tips -- DTC Codes C0561, P1629, P1682, U0101, U0121, U0155 and/or No Crank / No Start, HVAC, Radio, On-Star, Power Adjustable Pedals, and Other Electrical Components Inoperative |
Models: | 2007 Cadillac Escalade, Escalade ESV, Escalade EXT |
2007 Chevrolet Avalanche, Silverado, Suburban, Tahoe |
2007 GMC Sierra, Yukon, Yukon XL |
Attention: | This bulletin contains diagnostic information on the ignition switch and the GM LAN data lines. As these components and systems interact, it is possible to confuse one concern for another. Please read this entire bulletin before attempting repairs. |
Do This | Don't Do This |
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Perform the Vehicle Diagnostic System Check and Procedures in this bulletin. | Replace the ignition switch. |
If you encounter a no start / no crank concern and suspect an ignition switch fault, be sure to complete the Vehicle Diagnostic System Check as found in SI Document # 1741927. Be sure to check the power mode parameters in the BCM data display list in all ignition positions (Refer to the table in the SI document).
If any of the values read with the Tech 2® Diagnostic Scan Tool DO NOT match the values provided in the table, refer to "Power Mode Mismatch" (Document ID #1740479). You will find the relevant Connector End Views and pin numbers in Document #1740458. Complete an ignition component test. Check the resistance between the pins of the ignition switch (in all key positions) against the values provided in the resistance test table.
Important: DO NOT replace the ignition switch unless SI Diagnostics directs you to do so AND you have completed the checks below.
The type of customer concerns above may result from loss of the data stream on the GM LAN. One such cause is a short or grounding out of one of the data lines. Please follow the procedure below.
Parts are available through 3M at 1-800-364-3577.
Part Number | Description |
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06149 | Electrical Moisture Sealant Patches |
For vehicles repaired under the New Vehicle Warranty, please submit your claim for:
Labor Operation | Description | Labor Time |
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N6616 | Wiring And/Or Connector - Serial DATA/DLC/ONSTAR Connector - Repair Or Replace | 0.1-0.5 hr |