P0374: Timing Reference High Resolution Signal A No Pulses

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.

Medium severity. Can I keep driving?Drive as little as possible. If you feel jerking or the light flashes, stop: a misfire can damage the catalytic converter.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring of the coil indicated
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Check the condition of the spark plug
Swap the coil with another cylinder and see if the code changes
Measure the power supply and control signal using the manufacturer's wiring diagram

Good to know

Repair difficulty: hard
It can trigger limp mode.
It affects emissions.

What each character of P0374 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
3: Ignition and misfires
74: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0374?

Drive as little as possible. If you feel jerking or the light flashes, stop: a misfire can damage the catalytic converter.

What causes code P0374?

The most common causes are: sensor (pump or crankshaft) faulty or dirty; loose contact or interference in the signal wire; sensor disc or tone wheel damaged.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.