P2162: Vehicle Speed Sensor A/B Correlation
What to do
Say whether anything about the wheels or tyres has changed — new tyres, a different size, mismatched pairs, a space-saver spare left on. Two perfectly good sensors disagree permanently when the rolling radii differ, and no part will fix that. Otherwise, ask whether the ABS or stability system has stored codes of its own; that points at which of the two speed sources is the faulty one and saves paying to find out.
What this code means
The two independent road speed sources disagree by more than the module will tolerate. Both are producing a signal; neither is obviously wrong; they simply do not match.
This is the correlation argument the corpus makes for throttle and pedal sensors at P2135, applied to road speed — and it behaves the same way. The code names a relationship, not a part. Nothing in it says which of the two sources is at fault, and replacing either on a coin toss is a fifty per cent repair.
What narrows it is that the two sources are derived differently. One typically counts the transmission output shaft; the other is assembled from the wheel speed sensors by the braking system. So the disagreement can come from three places rather than two:
- The transmission-derived source is wrong — an output speed sensor or its ring, covered at P0720 and P0721.
- The wheel-derived source is wrong — one wheel sensor reading badly drags the average off.
- Neither is wrong and the vehicle has changed. Different rolling radii make a wheel-derived speed and a shaft-derived speed disagree permanently, with every sensor working correctly. That is the argument at P2159 and it is the first thing to eliminate here, because it is free.
A useful practical check: a wheel-derived error usually brings ABS or stability control fault codes with it, and a transmission-derived error usually does not. Which other systems have complained is therefore a real narrowing before anything is measured.
Likely causes
Start here
- Mismatched or incorrectly sized tyres · easy
- Faulty wheel speed sensor · moderate
- Faulty vehicle speed sensor · moderate
Less common
- Damaged reluctor or tone ring · specialist
- Damaged data bus wiring · specialist
- Incorrect final drive or tyre calibration after repair · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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