C0050 explained: The rear wheel speed signal, often from a single sensor on the rear axle or transmission tail housing, is missing or invalid. Sensor or harness is the usual cause.
🎯 Top Causes & Probability
55%
#1 - Most Likely
Failed Rear Axle Speed Sensor
Older RWAL trucks use one sensor at the rear axle or tail housing. They fail from heat and oil contamination.
🔨 Part
$30-$120
👨🔧 Labor
$60-$160
⚡ DIY
Easy
25%
#2 - Check First
Damaged Exciter Ring
Tone ring inside the differential loses teeth or rusts. Cover-off inspection is required.
🔨 Part
$80-$250
👨🔧 Labor
$220-$480
⚡ DIY
Hard
15%
#3 - Less Common
Harness Damage
Wire chafes against the driveshaft tunnel or rusts at the body junction.
🔨 Part
$10-$60
👨🔧 Labor
$80-$160
⚡ DIY
Medium
🚗 Most Affected Vehicles
🔧 Step-by-Step Diagnosis
- Locate the rear axle speed sensor, often at the tail housing or differential cover.
- Inspect the sensor wire for rub-throughs along the frame.
- Pull the sensor and check for metal debris stuck to the magnet.
- Measure sensor resistance and back-probe at the module for continuity.
- Replace the sensor or repair the harness as findings indicate.
❓ Frequently Asked Questions
Why does my old truck have only one rear sensor?
RWAL systems on 90s and early 2000s trucks use a single rear axle sensor. Four-wheel ABS came later on most pickups.
Is the sensor magnetic?
Yes. A small amount of metal debris on the tip is normal. Heavy buildup means it is time for a new sensor or differential service.
Will base brakes still work?
Yes. Only the rear-only ABS function is disabled.
How much fluid loss when pulling the sensor?
A few ounces of gear oil at most. Keep a rag handy and top off the differential after.