Redundant Brake System Fault
Indicates a failure in the redundant brake system of a vehicle.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer has detected a problem with one of the backup brake systems that help stop the truck safely.
What the computer is actually seeing
The ECU sees inconsistencies in the signal from the redundant brake sensors or modules, indicating a fault in brake pressure or control messages.
What a healthy reading looks like
Brake pressure should read between 70-100 psi when applied, and the redundant system should mirror this pressure within 5 psi.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the wiring and connectors related to the redundant brake system for damage or corrosion. If found, repair or replace as necessary. Decision: If wiring is damaged, repair and retest the system. If not damaged, proceed to step 2.
- 22. Check the brake pressure sensor operation. Use a scan tool to observe the brake pressure readings under normal conditions. Decision: If the readings are out of range, replace the sensor. If readings are normal, proceed to step 3.
- 33. Test the brake control module for faults. Use diagnostic software to check for active or pending codes in the module. Decision: If additional fault codes are present, address those codes accordingly. If no additional faults are present, replace the control module.
Common causes
- Wiring harness damage or shorts
- Faulty brake control module
- Failed brake pressure sensor
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
No, you should not drive the vehicle as the redundancy in the braking system may be compromised.
Will this fault code come back after repairs?
If repairs are done properly and the underlying issues are fixed, the code should not return.
Why does this code partner with SPN 1203?
SPN 1203 relates to the primary brake system, so failures in both could indicate broader issues with the vehicle's braking system.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →