Powertrain, generic · Ignition system or misfire

P0370 Timing Reference High Resolution Signal A

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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. Petrol engines practically do not use the code.

Likely causes

Optical sensor in the injection pump faulty (6.5-litre)
Wiring or connector between pump or sensor and module
Crankshaft sensor or tone wheel (LB7: 57X signal)
Injector driver module, engine module or CAN communication

Symptoms

  • Check engine light on
  • Loss of power (limp-home fuelling)
  • Rough running, hard starting, smoke
  • Stalling possible

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

high resolution timing sensorinjection pumpsensor wiringengine control modulecrankshaft position sensor

Related codes

P0371P0372P0373P0374P0335P0251

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.