Service Trailer Brake Message With DTC U0415 – 2014-2016 Chevrolet & GMC

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#PIT5490: Diagnostic Tip – Service Trailer Brake Message With DTC U0415 – (Jan 19, 2016)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern

Some owners may comment of a Service Trailer Brake message in the DIC.  When checking for DTC’s, a U0415 “Invalid Data Received From Electronic Brake Control Module” may be set in the Chassis Control Module.  It may also be noticed that this message occurs during hard braking, acceleration and/or turns.

This concern could be caused by the brake fluid level near the minimum level.  The brake fluid level sensor may momentarily signal the brake fluid level is low as the brake fluid sloshes in the master cylinder reservoir during hard braking, acceleration and/or turns.  The brake fluid level sensor is a direct input to the EBCM.  The EBCM sends the brake fluid level data to the Chassis Control module via the High Speed LAN communication buss.  When the Chassis Control Module received the message that the brake fluid level was low, it sets DTC U0415 and commands the “Service Trailer Brake” message on.

The brake fluid level sensor data can be monitored using the Scan Tool (GDS2) under the EBCM Antilock Braking Data list parameter “Brake Fluid Level Sensor”.  It will display either “OK”  or “Low”.

Recommendation/Instructions

Fill the master cylinder brake fluid reservoir to the maximum level.

Note: The brake fluid level could be low due to normal brake pad wear, leaks, etc.  Inspect the truck to determine why the brake fluid level was low.  If no brake fluid leaks are found and it is not the result of brake pad wear, inspect the rear of the master cylinder to determine if it may be leaking into the brake booster.  Refer to Brake Fluid Loss in SI.

Warranty Information

The correction for this concern may be one of several repairs described above.  For vehicles repaired under warranty, please use the appropriate warranty labor operation based on the actual cause and repair.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

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