P0377
Timing Reference High Resolution Signal B Too Few Pulses
The appearance of the standard OBD2 trouble fault code P0377 is an indicator that your vehicle ECU triggered a threshold alert for "Timing Reference High Resolution Signal B Too Few Pulses". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Storing code P0377 is your car's way of telling you something is wrong with the timing reference high resolution signal b too few pulses. The most common signs are misfire, lack of power, engine shutdown. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Misfire, lack of power, engine shutdown
Common Causes
- Damaged reluctor ring teeth
- Failing sensor B
- High resistance in signal wire
- Loose sensor mounting
How to Fix
- 1 Replace reluctor ring
- 2 Replace sensor B
- 3 Repair wiring resistance
- 4 Tighten sensor bracket
Technical Explanation
P0377 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including damaged reluctor ring teeth — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
The most common mistake with P0377 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Sensor replacement: 150 - 400