Front Steering Position Sensor Circuit (Steering Wheel Position Sensor / SWPS)

What C0455 means

C0455 is set by a General Motors control module (the electronic brake control module or, on Quadrasteer trucks, the rear-wheel-steering module) when it sees an out-of-range or illogical signal from the steering wheel position sensor. That sensor reports steering angle with one analog output and three digital outputs (Phase A, Phase B and a marker/index pulse). The analog line sits near 2.5 volts with the wheel centered and sweeps from roughly 0.25 volt at full left to 4.75 volts at full right; each Phase A/B transition equals about one degree of rotation. The module flags C0455 when a phase or marker circuit reads open, shorted to ground, or shorted to voltage, or when the angle changes more than 30 degrees with no matching signal change. Because a C-code is manufacturer-specific, C0455 varies by make: on GM it is this steering-position sensor circuit tied to stability control, while some code lists instead map it to an electric power steering assist-motor circuit. Read the meaning against the vehicle that stored it.

Symptoms

• Service StabiliTrak or Service Traction Control message shown in the driver information center
• StabiliTrak, traction control, and often ABS warning lights illuminated
• Stability and traction control disabled, so the system no longer intervenes
• Steering-angle data on a scan tool reads erratic, frozen, or implausible
• On Quadrasteer trucks, a Service 4-Wheel Steer message with the rear wheels returned to center
• On applications where the code is mapped to the EPS motor, heavier or intermittent steering assist

Common causes

• Corroded or loose SWPS connector (fretting corrosion), the most common cause per GM bulletin PI0639
• Failed steering wheel position sensor
• Open, short-to-ground, or short-to-battery fault in a Phase A, Phase B, or marker-pulse circuit
• High-resistance or poor connection at the control module (EBCM / rear-wheel-steering module / BCM) connector
• Serial-data (Class 2) communication fault or a companion BCM code such as C0472/C0473
• On EPS-equipped applications, low charging/system voltage or a failing torque/position sensor feeding the assist motor

Severity & driving advice

Severity: Moderate — Base steering and brakes still work, but StabiliTrak, traction control, and steering-angle input drop out until the SWPS circuit is repaired.

Can I drive? Drivable, but stability control is off; fix soon.

Diagnostic approach

1. Confirm the code and inspect the connector first — Scan all modules and record every stored code, then inspect and re-seat the SWPS connector. GM bulletin PI0639 attributes most C0455 complaints on 2007-2014 trucks and SUVs to fretting corrosion at this connector, so cleaning terminals and applying dielectric grease is a low-cost first move before any parts.
2. Determine current versus history status — Note whether C0455 is current or history. On these systems the module shuts off the 12-volt reference to the SWPS while the fault is current, so all digital signals and reference voltages read low and live data is unreliable. Cycle the ignition to make it a history code before monitoring data, or the readings will mislead the diagnosis.
3. Check for companion module codes — Look for related BCM codes such as C0472 or C0473. If those are present, diagnose them first, because a steering-angle supply or reference problem upstream can force C0455. Rule out a Class 2 serial-data communication fault at the same time.
4. Test the SWPS supply, reference, and signal circuits — Back-probe the sensor and verify the battery-voltage and ground circuits, then confirm the analog signal sits near 2.5 V centered and sweeps 0.25 V (full left) to 4.75 V (full right). While rotating slowly over center, the Phase A/B circuits should switch between about 0.080-0.180 V and 10.5-12.0 V; a circuit stuck high points to a short to voltage, one stuck low points to an open or short to ground.
5. Isolate wiring versus sensor and repair — If circuit tests fail, repair the open/short in the identified Phase A/B, marker, supply, or ground wire. If the circuits and connections are good but signals are wrong, replace the SWPS; if the sensor and wiring check out, suspect the control module. After replacing a sensor or module, clear codes and perform the steering-angle/alignment relearn.

Make & model notes

GM (Chevrolet, GMC, Buick): C0455 is Front Steering Position Sensor (SWPS) Circuit, common on 2007-2014 trucks and SUVs; bulletin PI0639 blames connector fretting corrosion. Inspect and secure the connector before replacing the sensor.

Other makes: C-codes are manufacturer-specific. On non-GM vehicles C0455 may be undefined or point to a different steering circuit, and some code lists map it to an electric power steering assist-motor circuit. Verify against the vehicle that set it.

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