C1233
Left Front Wheel Speed Input Signal Missing
Findings, check these first
- Failed left front wheel speed sensor
- Damaged sensor wiring chafed by the suspension or tire
- Cracked or missing tone ring tooth on the hub or axle
- Excessive wheel bearing play changing the sensor gap
- Corroded ABS module connector pins
Standard procedure
- Read all four wheel speeds on a scan tool during a slow roll test
- Inspect the left front sensor wiring along its full suspension routing
- Check the tone ring for cracks, missing teeth and debris
- Test wheel bearing play. Replace the hub if loose
- Replace the sensor after confirming its air gap and circuit
Code lookup
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Sources and review
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Last updated 2026-09-25.
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This fault is part of the Ford ABS and traction control codes guide. It covers the family and the order to check it.