How severe is fault code C1235?

Serious — Stop or limit driving

OBD Code C1235: Speed Wheel RR Input Signal Missing

Q: What does OBD code C1235 mean?

Speed Wheel RR Input Signal Missing. Your vehicle's right rear wheel speed sensor isn't sending a signal to the ABS/stability control system. Think of it like one corner of your car going blind—the system can't see how fast that wheel is spinning.

Q: What are the symptoms of fault code C1235?

ABS warning light illuminated on dashboard, Traction control or stability control disabled, Reduced braking performance or wheel lockup during hard stops

Q: How do I fix OBD fault code C1235?

Inspect the RR wheel sensor connector for corrosion, dirt, or loose pins and clean or reseat as needed.. Check the wiring harness from the RR wheel to the ABS module for damaged insulation, pinches, or disconnections and repair or replace.. Replace the RR wheel speed sensor if connector and wiring are intact and no signal is detected with a multimeter.

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What This Actually Means

In plain language — no jargon

Your vehicle's right rear wheel speed sensor isn't sending a signal to the ABS/stability control system. Think of it like one corner of your car going blind—the system can't see how fast that wheel is spinning.

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Symptoms You May Notice

3 known symptoms for this code

ABS warning light illuminated on dashboard

Traction control or stability control disabled

Reduced braking performance or wheel lockup during hard stops

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Embedded Systems Insight

What the ECU/ECM is actually computing

The ECU monitors voltage pulses from the right rear wheel speed sensor, which generates a signal proportional to wheel rotation. The system expects a continuous AC signal within a specific frequency range when the vehicle is moving. If the signal drops to zero or falls below the minimum threshold for more than a brief moment, the fault is triggered.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Wheel Speed Signal Frequency	Continuous AC signal 50-5000 Hz (varies by speed)	Signal absent or below 5 Hz for >2 seconds while driving
Signal Voltage Amplitude	0.2-5V peak-to-peak	<0.05V or completely absent

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Wheel speed sensor connector

Inspect the RR wheel sensor connector for corrosion, dirt, or loose pins and clean or reseat as needed.

2

Wheel speed sensor wiring harness

Check the wiring harness from the RR wheel to the ABS module for damaged insulation, pinches, or disconnections and repair or replace.

3

Right rear wheel speed sensor

Replace the RR wheel speed sensor if connector and wiring are intact and no signal is detected with a multimeter.