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P0377 – Timing Reference High Resolution Signal B Too Few Pulses (OBD2)

P0377 means "Timing Reference High Resolution Signal B Too Few Pulses". The crankshaft position sensor delivers the wrong number of pulses or erratic pulses, so the control unit cannot trust the timing information.

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P0377 quick summary

Fault codeP0377
MeaningTiming Reference High Resolution Signal B Too Few Pulses
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?Not recommended. A failing crankshaft sensor can make the engine stall without warning – including in traffic – and it may not restart.
Repair cost€30 – €400

How the crankshaft position sensor works

The crankshaft position sensor tells the engine control unit how fast the engine turns and exactly where the pistons are – without it, most engines cannot start.

The sensor reads a toothed reluctor ring on the crankshaft or flywheel. A gap of one or two missing teeth marks a reference position. Older sensors are inductive (they generate an AC voltage), newer ones are Hall sensors with a 5 V or 12 V supply and a square-wave signal.

The engine control unit uses the signal for ignition and injection timing, engine speed, misfire detection and, together with the camshaft sensor, to identify which cylinder is on its compression stroke. Some systems use a second crankshaft signal (sensor B) or a high-resolution timing signal (P0370–P0379).

A failing crankshaft sensor often causes the engine to cut out when warm and restart after cooling down, or prevents starting altogether. Damaged reluctor rings, metal debris on the sensor tip and wiring damage are common causes besides a failed sensor.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16761 (P0377). Both numbers mean the same fault.

Symptoms of P0377

  • Engine cranks but does not start
  • Engine cuts out, often when warm, and restarts after cooling down
  • No rev counter movement while cranking
  • Misfires or jerking
  • Check Engine light on

Most common causes of P0377 (most likely first)

Mechanic's Pro Tip

If the engine cuts out only when hot, check the crankshaft sensor first – and test it while it is hot. A heat gun on the sensor or a test drive with live data often reproduces the fault that disappears once the engine cools down.

  1. 1.Electrical interference

    Most likely

    Damaged shielding, aftermarket ignition parts or a poor ground can add false pulses.

  2. 2.Damaged reluctor ring or wrong sensor air gap

  3. 3.Faulty crankshaft position sensor or loose connector

  4. 4.Metal debris on the sensor tip

    Magnetic sensors attract particles from wear, which distort the signal.

Step-by-step diagnostic guide

  1. 1

    Read codes and check rpm while cranking

    Read all codes. While cranking, check whether the scan tool or rev counter shows engine speed – no rpm while cranking points strongly to the crankshaft signal.

  2. 2

    Look at the signal on an oscilloscope

    Record the crankshaft position sensor signal while cranking and running. Missing, extra or distorted pulses show whether the problem is the sensor, the reluctor ring or interference. Check the shielding and grounds.

  3. 3

    Inspect the sensor and tip

    Remove the sensor and look for debris, damage or oil in the connector. Clean the tip and check that it sits correctly.

  4. 4

    Measure the sensor

    Check supply and ground on Hall sensors; measure resistance and AC output on inductive sensors.

    Multimeter: Inductive sensors: often a few hundred to about 1,000 Ω and an AC voltage of roughly 0.5 V or more while cranking. Hall sensors: 5 V or 12 V supply and a switching square-wave signal.

  5. 5

    Check signal quality

    With an oscilloscope, look for missing, distorted or irregular teeth. A damaged reluctor ring shows as a repeating error at the same position.

  6. 6

    Replace and relearn

    Replace the sensor or repair wiring. Some engines need a crankshaft variation relearn (see P0315) after replacement.

Frequently asked questions

Can I keep driving with P0377?

Not recommended. A failing crankshaft sensor can make the engine stall without warning – including in traffic – and it may not restart.

How much does it cost to fix P0377?

Typical repair costs are 30 € – 400 €, depending on the cause and the vehicle. The most common fixes are: electrical interference; damaged reluctor ring or wrong sensor air gap; faulty crankshaft position sensor or loose connector. Always confirm the cause with the tests above before buying parts.

Can a car start with a bad crankshaft sensor?

Usually not. Some engines can use the camshaft signal as a backup and start after long cranking, but most will not run without a crankshaft signal.

What is the difference between crankshaft and camshaft sensors?

The crankshaft sensor gives engine speed and piston position; the camshaft sensor tells which stroke the cylinder is on. The engine needs both for precise injection and ignition, but the crankshaft signal is the more critical.

What is the difference between P0377 and similar codes?

P0377 belongs to a group of codes for the same component that differ in the type or location of the fault: P0374 – Timing Reference High Resolution Signal A No Pulses; P0375 – Timing Reference High Resolution Signal B Malfunction; P0376 – Timing Reference High Resolution Signal B Too Many Pulses; P0378 – Timing Reference High Resolution Signal B Intermittent/Erratic Pulses; P0379 – Timing Reference High Resolution Signal B No Pulses; P0385 – Crankshaft Position Sensor B Circuit Malfunction. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.