C1236 on Mercury

Left rear wheel speed sensor input missing (Ford)

Severity: Inspect soon

The ABS lamp is on and ABS is off, and on Windstars the code appears with a failing ABS module and a brake warning light.

It gets more serious if:

Stop: Stop and have the vehicle inspected if a red BRAKE warning light comes on or the brake pedal feels different.

Safety-critical system: explanation only, no DIY steps. Source: how we rate severity

This page covers only what differs on Mercury. For what C1236 means, the ranked causes and the test order, see the C1236 guide.

What's different on Mercury

Mercury

2004 · Mountaineer
Supported by vehicle data
Bulletin 03263 covers C1235/C1236/C1237 with a differential-mounted sensor.

03263Status unverified
ABS lamp with C1235, C1236, C1237
2004mountaineer · issued July 26, 2004 · NHTSA 10008281
Vehicles with differential-mounted rear sensor; summary only.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Sources and review

Mercury 03263: ANTI-LOCK BRAKE SYSTEM (ABS) LAMP ILLUMINATED AND DIAGNOSTIC TROUBLE CODE (DTC) C1235, C12 — NHTSA manufacturer communications (flat file, NHTSA ID 10008281)
NHTSA complaint ODI 10217805: 2003 Ford Windstar, C1236 LR wheel speed sensor input missing — NHTSA Office of Defects Investigation
NHTSA complaint ODI 10274301: 2002 Ford Windstar ABS codes — NHTSA Office of Defects Investigation

Last reviewed: October 16, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error