P0370 code meaning
Timing Reference High Resolution Signal A
Powertrain system Generic code P03xx codes Check engine light
What P0370 means
Some diesel systems give the injection control a finely divided angle signal in addition to the normal reference signal, to time and meter injection precisely – the high resolution signal. GM's 6.5-litre diesel (1997) had an optical sensor in the injection pump that delivers a high resolution track and one cam reference pulse per cylinder; P0370 is set if more than 8 consecutive cam pulses pass without progress on the high resolution counter, in the first trip. The engine then runs on backup fuelling with reduced power, and injection timing control is suspended. On the 2004 Duramax LB7 the injector driver module evaluates the 57X crank signal and reports 'no crank signal' over CAN; from 60 rpm, 100 of 120 samples sets P0370, also in the first trip. Gasoline engines practically do not use the code.
P0370 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0370
- Check engine light on
- Loss of power (limp-home fuelling)
- Rough running, hard starting, smoke
- Stalling possible
Common causes of P0370
- Most likelyOptical sensor in the injection pump faulty (6.5-litre)
- PossibleWiring or connector between pump or sensor and module
- PossibleCrankshaft sensor or tone wheel (LB7: 57X signal)
- Less likelyInjector driver module, engine module or CAN communication
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
High resolution timing sensorInjection pumpSensor wiringEngine control moduleCrankshaft position sensor
What each part of P0370 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3 | Area: ignition system or misfire. |
| 70 | The exact fault in that area. |
What to do next
- Note P0370 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0370
What does P0370 mean?
P0370 means "Timing Reference High Resolution Signal A". Some diesel systems give the injection control a finely divided angle signal in addition to the normal reference signal, to time and meter injection precisely – the high resolution signal. It is a generic code, so it means the same on every make.
Is it safe to drive with P0370?
Drive gently and only to a workshop. With P0370 the car can go into limp mode (reduced power) to protect itself.
Will P0370 fail an emissions test?
Yes, it can. P0370 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0370 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P0370 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.