What Does C1289 Mean?
The redundant (secondary) brake pressure transducer input circuit has failed. This is the backup pressure sensor in a dual-circuit braking system, typically monitoring the secondary hydraulic circuit (usually rear brakes). The redundant sensor provides a safety cross-check for the primary sensor. Without it, the system loses its ability to verify brake pressure readings and may disable certain advanced braking features.
Common Causes
35%
Failed secondary brake pressure transducer (internal sensor failure)
25%
Wiring fault in the secondary transducer circuit (open, short, or high resistance)
20%
Connector corrosion or brake fluid contamination at the secondary sensor
10%
Shared 5V reference supply failure affecting the secondary sensor
10%
EBCM input circuit fault for the secondary pressure channel
Diagnostic Steps
1
Monitor the secondary brake pressure PID in live data alongside the primary pressure PID — both should track together proportionally when the brake pedal is pressed. If the secondary is absent or erratic while the primary works normally, the fault is isolated to the secondary circuit.
2
Check for 5V reference and ground at the secondary transducer connector. If the same 5V supply feeds both transducers, verify the primary sensor did not pull the reference low (disconnect primary to test).
3
Measure the secondary transducer signal output with a voltmeter — approximately 0.5V at rest, rising proportionally with pedal pressure to about 4.5V at maximum.
4
Inspect the secondary transducer connector for brake fluid contamination (DOT fluid attacks plastic housings and corrodes terminals). Clean with brake cleaner and apply dielectric grease.
5
Test wiring continuity from the secondary transducer connector to the corresponding EBCM pins. Pay attention to the harness routing near the master cylinder and HCU where brake fluid leaks can damage wires.
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
The redundant (secondary) brake pressure transducer input circuit has failed. This is the backup pressure sensor in a dual-circuit braking system, typically monitoring the secondary hydraulic circuit (usually rear brakes). The redundant sensor provides a safety cross-check for the primary sensor. Wi...
The most common cause of C1289 (Pressure Transducer Redundant / Secondary Input Circuit Failure) is: Failed secondary brake pressure transducer (internal sensor failure)
Typical repair costs for C1289 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Basic braking remains fully functional. The redundant pressure sensor provides a safety cross-check; without it, the system cannot verify primary sensor accuracy. Some advanced braking features (Brake Assist, dynamic rear proportioning) may be limited. The vehicle is safe for normal driving, but repair should be scheduled soon to restore full system redundancy.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1289 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Brake Assist
Difficulty
Type
Manufacturer
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