OBD-II trouble code
P0370: Timing Reference High Resolution Signal 'A' Malfunction
Some engines take two crankshaft references — a coarse one and a fine one. This code is about losing the fine one, and the jobs that depend on it are not the ones most people expect.
Quick facts
- System
- Powertrain
- Category
- Sensors / Timing
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $150 – $1,200
- DIY difficulty
- Advanced DIY
What does P0370 mean?
The words that matter in this code's title are 'high resolution', and they describe an architecture that not every engine uses. Systems that set this code take two separate timing references from the rotating assembly. One is coarse: a handful of pulses per revolution, enough for the module to know roughly where the crankshaft is and to work out engine speed. The other is fine, delivering many more pulses per revolution and letting the module know crank angle to within a fraction of a degree at any instant.
What the fine reference buys is precision in three specific jobs, and none of them is simply keeping the engine running. The first is injection timing, which matters most on high-pressure direct injection and diesel systems where an injection event lasts a fraction of a millisecond and its position in the cycle determines both power and emissions. The second is knock windowing: the module only listens to the knock sensor during the narrow crank angle window in which real detonation can occur, and it needs fine resolution to know when that window opens. The third is the one with the longest tail — misfire detection. The module identifies a misfire by measuring how much the crankshaft slows between firing events, and those differences are tiny. Without a high-resolution signal the measurement is simply not possible.
That third dependency creates a consequence unique to this code. When the high-resolution signal goes, misfire monitoring goes with it, and the misfire monitor is one of the readiness monitors an emissions test checks. A vehicle can have this fault repaired correctly and still fail an inspection afterwards, because the monitor stays flagged not-ready until the car has completed enough driving for it to run and pass. Plan for a few days of ordinary mixed driving between the repair and the test rather than booking them for the same afternoon.
Where the signal physically comes from varies more than you might expect, and it decides the repair. Some engines carry a second, finer-toothed reluctor track on the crankshaft with its own dedicated sensor. Others take the high-resolution reference from the camshaft or from an optical pickup inside the distributor, where a slotted disc spins between a light source and a photodetector — an arrangement that has its own distinctive failure mode, because oil mist or debris settling on the disc or the optics degrades the signal with nothing electrically wrong anywhere. Establish which arrangement you have before ordering a part.
Whether the engine keeps running is genuinely hard to predict. Some strategies fall back on the coarse reference and run in a degraded, protected mode; others treat the loss as fatal and stop. Do not assume yours is the forgiving kind.
Common causes
- Failed sensor reading the high-resolution reference track
- Oil, debris or condensation contaminating the disc or optics of an optical pickup
- Damaged, chipped or contaminated high-resolution reluctor track
- Open, shorted or chafed wiring in the high-resolution signal circuit
- Corroded or poorly seated connector at the sensor or distributor
- Incorrect air gap from a sensor that is not fully seated or is the wrong part number
- Failed ignition or fuel injection control module on systems where it conditions this signal before passing it on
- Poor shielding or a broken shield ground allowing interference onto a signal that carries far more pulses than the coarse reference
Symptoms
- Check engine light on, sometimes with the engine still running acceptably
- Hard starting, extended cranking or a complete no-start
- Engine stalling, either at idle or without warning while driving
- Reduced power and duller response as the module runs a protected fallback strategy
- Rough running or hesitation, particularly on a direct injection or diesel engine
- Misfire readiness monitor showing not ready, which can cause an emissions test failure
Diagnostic steps
- 1.Establish where the high-resolution reference comes from on this engine: a dedicated fine-toothed track on the crankshaft, a camshaft source, or an optical pickup in the distributor. The repair is different in each case.
- 2.Read all stored codes together. A coarse reference or camshaft code alongside this one usually indicates a shared supply, ground or harness branch rather than two separate failures.
- 3.Check the readiness monitor status while you are connected, so the emissions consequence is known up front rather than discovered at the test station.
- 4.If the source is an optical pickup, inspect the disc and the optics for oil mist, debris and condensation before testing anything electrically. Contamination degrades the signal with no electrical fault present.
- 5.Put the high-resolution signal on a scope and count pulses against the coarse reference over one revolution. Missing or extra pulses are the finding; a multimeter cannot see either.
- 6.Confirm the sensor's supply and ground at its own connector rather than at the module, so the wiring between them is inside the test.
- 7.Inspect the shield and its ground connection. A signal carrying this many pulses is more vulnerable to interference than the coarse reference, and a broken shield ground is a real cause.
- 8.Remove the sensor and inspect its tip and the reference track for debris, chipped teeth and impact damage before fitting a replacement.
Repair cost
$150 – $1,200
A dedicated sensor is commonly $40 to $200 in parts and $150 to $450 fitted where access is reasonable. An optical distributor pickup is the more expensive route, often sold only as a complete distributor at $150 to $600 in parts plus fitting and timing, so $350 to $900 is realistic. Wiring, connector and shield ground repairs are the cheapest outcome at $100 to $350. Damage to the high-resolution reference track itself is the worst case and can require major disassembly. Allow a few days of ordinary driving after the repair for the misfire readiness monitor to run before an emissions test.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with crankshaft position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an advanced DIY job. It typically requires specialty tools, scan-tool access, lifting equipment, or careful sequencing to avoid causing new failures. Plan for extended downtime and have a backup vehicle. Most owners are better served by a shop that has done this repair before.