Hello I have a 2000 GMC Yukon Denali that is intermittently

A 2000 GMC Yukon Denali is experiencing intermittent power loss to the radio, power windows, and windshield wipers. These components are all powered by the RAP relay; however, the possibility of the relay failing at random intervals seems unlikely. There is a concern that the Body Control Module (BCM) may be malfunctioning. The issue has been observed to occur without a discernible pattern, sometimes not happening at all and other times cycling on and off several times per minute. Initially, the problem was triggered by pressing the window button, but it has since escalated to occurring without any input, regardless of whether the radio is on or off. Preliminary checks on the power window wiring and grounds have not revealed any faults. Notably, when the system is tripped, locking and unlocking the doors quickly can sometimes restore functionality, but this is not consistent. Service documents indicate that there is no RAP relay; instead, the BCM controls power to the affected components, suggesting that a BCM issue could be a possibility. More commonly, loose connectors or fuses may be the culprit, particularly when the vehicle encounters bumps or temperature fluctuations that can cause connectors to expand and contract. It is advisable to inspect the main fuse socket (IGN B) and the BCM connectors for any loose connections, especially the Dark Blue wire at pin C2 of Connector C2. The C304 connector pins B9 and G2 are of particular interest as they manage power in and out. This is an inline connector that may also be suspect. Wiggling the wires and connectors may help reproduce the problem, and a test light or multimeter would be useful for troubleshooting.

A comprehensive approach to diagnosing the power loss issue in the 2000 GMC Yukon Denali involves a systematic examination of the electrical system, particularly focusing on the Body Control Module (BCM) and its associated wiring. The BCM is integral in managing various electrical components within the vehicle, including the radio, power windows, and wipers. Given the symptoms described, it is essential to begin with a visual inspection of the BCM connectors for any signs of corrosion, dirt, or physical damage. The connections should be securely seated, and any loose wires should be addressed.

Next, utilize a multimeter to verify the voltage levels at the BCM input and output pins. Pay close attention to the pins B9 and G2 of the C304 connector, as these are critical for power distribution. If voltage is inconsistent or absent, further investigation into the wiring harness leading to the BCM may be necessary. Inspect for frayed wires or damaged insulation, particularly in areas where the harness may be subjected to movement or abrasion.

In addition, the main fuse socket (IGN B) should be thoroughly checked for integrity. A loose or corroded fuse can lead to intermittent power issues. If the fuse appears to be in good condition, ensure that the socket itself is clean and free of debris.

Given the intermittent nature of the problem, it is prudent to simulate conditions that may exacerbate the issue. This can include driving over rough terrain or varying temperature conditions to observe if the power loss occurs under these circumstances. Documenting the conditions under which the problem arises may provide valuable insights into the underlying cause.

If all physical inspections yield no results, consider testing the BCM itself. This may involve using a diagnostic scanner to check for any fault codes related to the BCM or the affected components. If no codes are present, but the issue persists, it may be necessary to replace the BCM as a last resort.

In summary, a methodical approach to diagnosing the electrical issues in the 2000 GMC Yukon Denali is essential. By focusing on the BCM, its connectors, and the associated wiring, it is possible to identify the root cause of the intermittent power loss and implement an effective solution.A 2000 GMC Yukon Denali that is intermittently losing power to the radio, power windows and wipers. I know these are all fed from the RAP relay but I find it hard to believe the relay could be failing at such random intervals with no apparent pattern. Could the BCM be failing If so how can I check this Any help would be appreciated, it`s driving me crazy!

Thanks, Josh I haven`t been able to check much. Just tried to recognize a pattern, but there doesn`t seem to be one. Sometimes it doesn`t happen at all and sometimes it cycles on/off a couple times a minute. It started by tripping when you pushed the window button but now will do it without touching anything and with the radio on or off. At first I checked the power window wiring and grounds but I can`t find anything wrong (obviously). One more thing, when it`s tripped sometimes you can get to come on by locking/ unlocking the doors quickly, but not always.

According to the service documents, there is no RAP relay. The control of the power to the components you mentioned is done by the BCM, so yes, it could be a problem with that module. But what is more common is that a connector or fuse is coming loose, especially when the vehicle goes over bumps or there are temperature changes (connectors expand & contract).

In the mean time, I would check the socket of that main fuse (IGN B), and if you have access to the BCM connectors, see if there are any "obvious" loose connectors or wires, especially the Dark Blue wire at pin C2 of Connector C2. Here are the connector C304 pins. Pins B9 & G2 are where the power comes out and in, and are the pins of interest. This an "inline" connector, and is also suspect. You might want to wiggle these wires and connectors and see if you can reproduce the problem. A test light or multimeter would also be handy for troubleshooting. Ask-a-doc Web sites: If you`ve got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers.

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