Powertrain, generic (extended)

P2162 Vehicle Speed Sensor A/B Correlation

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P2162 means two speed sources, A and B, disagree by more than the calibration permits although each circuit is electrically sound. Depending on the vehicle, A and B can be a transmission output sensor, a transfer case sensor or wheel sensors read through the ABS unit. No manufacturer documents P2162 publicly. GM shows how closely the sources are linked: when its transfer case sensor fails (P2160/P2161), the software substitutes driven-wheel speed multiplied by the axle ratio (18OBDG04). California's OBD rule names the vehicle speed sensor among inputs that must be checked for plausibility. Wrong tyre size or axle ratio, a damaged tone wheel or debris on one sensor are typical causes. Speedometer, shifting, cruise control and 4WD may suffer.

Likely causes

Tyre size or axle ratio differs from the programmed values

Metal debris or damage on one of the two sensors

Damaged or wrong tone wheel on one shaft or hub

Wheel speed signal from the ABS unit faulty

Symptoms

Check engine lamp
Speedometer reading wrong or unsteady
Harsh or mistimed shifts, possibly a fixed-gear fallback

Repair estimate

DifficultyMediumDIY possible

Parts and labour€0–450

Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

vehicle speed sensorvehicle speed sensor b

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org.