Powertrain, generic · Ignition system or misfire

P0374 Timing Reference High Resolution Signal A No Pulses

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 – the high resolution signal. By its J2012 name P0374 means signal A delivers no pulses at all although the engine turns. GM's 2004 Duramax LB7 uses the code differently, for a plausibility fault: the injector driver module evaluates the 57X crank signal and reports it as implausible over CAN; from 60 rpm, 100 of 120 samples of 31.6 ms set the code, in the first trip. GM's 6.5-litre diesel with the optical sensor in the injection pump reports all faults of its high resolution track under P0370. Without the fine signal the module falls back to coarser timing, so the engine loses power and may run roughly or start poorly.

Likely causes

Sensor (pump or crankshaft) faulty or dirty

Loose contact or interference in the signal wire

Sensor disc or tone wheel damaged

Injector driver module or engine module

Symptoms

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

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

P0370 P0371 P0372 P0373 P0335

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