P0319
Rough Road Sensor B Signal Circuit
Encountering the engine check light code P0319 signifies an explicit mechanical or electrical operational breakdown categorized as "Rough Road Sensor B Signal Circuit". Professional scanner tools usually flag this subsystem loop early on.
Driver's Summary
P0319 is triggered when the PCM detects an abnormal condition associated with rough road sensor b signal circuit. You may notice pcm fails to suspend misfire monitoring on bumpy roads, false codes, all of which are direct consequences of this malfunction. This is a low-urgency fault with minimal immediate impact on safety, but it should be resolved before your next emissions test.
Symptoms
PCM fails to suspend misfire monitoring on bumpy roads, false codes
Common Causes
- Defective rough road sensor B
- Open circuit in sensor B wiring
- Water intrusion in connector
- ABS/EBCM fault
How to Fix
- 1 Test and replace sensor B
- 2 Repair wiring harness
- 3 Dry connector and apply dielectric grease
- 4 Scan ABS module for faults
Technical Explanation
To set P0319, the PCM samples the affected circuit multiple times per second, comparing live readings against manufacturer-programmed operating windows. Misfire rate is counted per cylinder over rolling windows and compared against two thresholds: a catalyst-damaging rate (triggers flashing MIL) and an emissions-exceeding rate (triggers solid MIL). The PCM logs which cylinder is misfiring based on crankshaft position at the time of each detected event. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
Immediate safety risk is low with P0319 active. The primary concern is regulatory — this fault will cause a failed emissions test — and the secondary risk is that the small root cause (defective rough road sensor b) becomes a larger problem if ignored for months.
Mechanic's Pro Tip
Before replacing any component on P0319, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Sensor replacement: 100 - 250