What causes a P1502 code?

P1502 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P1502 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1502 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

OBD-II

P1502

Vehicle speed pulse width modulated mark/space ratio

What it means

The ECM has detected an invalid or out-of-range pulse width modulated signal for the vehicle speed, indicating the duty cycle of the signal does not match expected parameters.