Vehicle Speed Sensor "A" Circuit Low Input
The POWERSTROKE-P0502 (Power Stroke) diesel fault code means: Vehicle Speed Sensor "A" Circuit Low Input. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- beginner
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What Are the Symptoms of POWERSTROKE-P0502?
- Check Engine Light on
- Speedometer reads zero or drops out
- Possible shifting problems
What Causes POWERSTROKE-P0502? (Most Likely First)
- Failed speed sensor High
- Open or shorted signal wiring High
- Corroded connector Moderate
Can I Still Drive with POWERSTROKE-P0502?
Yes, but fix soon. POWERSTROKE-P0502 is rated moderate severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring it.
Frequently Asked Questions
What does P0502 mean on a Power Stroke?
P0502 means Vehicle Speed Sensor "A" Circuit Low Input. The speed signal from sensor "A" is below its normal range or missing while the truck is moving.
Is P0502 a Power Stroke-specific code?
No. P0502 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions Ford uses to set it on its diesels are in Ford service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose POWERSTROKE-P0502?
Inspect the sensor connector and harness.
Check the sensor output while turning the driveline or driving.
Check the circuit for opens and shorts to ground.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P0502 as a generic OBD-II code)
P0502 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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