What it means
A general electrical fault on the high-resolution timing reference signal A — used by ignition and injection systems for precise crank angle measurement (typically a 60-2 or 36-1 tone wheel signal).
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module uses timing reference signal A to track crankshaft position and coordinate ignition and fuel injection. This code sets when the signal has an electrical fault that prevents the module from reading it reliably, without identifying a specific pulse-count or no-pulse condition.
Common causes
Most likely first.
- Timing reference sensor failure
- Damaged, loose, or corroded wiring or connector
- Damaged or incorrectly aligned reluctor/tone wheel
Symptoms
- Check engine light on
- Hard starting or no start
- Engine stalling or rough running
- Power loss
How to diagnose it
- Save freeze-frame data and check live engine-speed data while cranking to see whether the module detects a usable timing signal.
- Inspect signal A's sensor connector and wiring for looseness, corrosion, damage, or contact with hot or moving parts.
- Check the sensor and its power, ground, and signal wiring using the vehicle wiring diagram, looking for opens, shorts, or poor connections.
- Compare the signal waveform during cranking with the manufacturer's specification to distinguish a sensor or circuit fault from an irregular target.
- Inspect signal A's reluctor or tone wheel for damage, misalignment, or an incorrect installation, then recheck the signal.
Common fixes
- Reconnect or clean a loose or corroded signal A connector.
- Repair damaged or poorly routed signal A wiring.
- Replace the timing reference sensor for signal A if its output fails the specified test.
- Repair or correctly align the signal A reluctor or tone wheel if it is damaged or misaligned.
Can I keep driving?
Avoid unnecessary driving if the engine is stalling, running roughly, or losing power; it may become difficult to restart or stop unexpectedly. If it runs normally, drive only as needed to reach a safe place for diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.