OBD-II trouble code
P0319: Rough Road Sensor "B" Signal Circuit
A second rough road input is failing. Before testing anything, establish whether that second input is a physical device on this vehicle or a value arriving over the network from the brake system — the two lead to completely different repairs.
Quick facts
- System
- Powertrain
- Category
- Ignition / Misfire
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,200
- DIY difficulty
- Shop recommended
What does P0319 mean?
The presence of this code tells you something before any testing begins: the engine controller's calibration expects two rough road inputs rather than one. What it does not tell you is what the second one physically is, and that question governs the entire repair.
There are two common architectures. On a minority of applications there really is a second accelerometer, generally mounted at a different point on the structure or on a different axis, so that the controller can distinguish surface roughness from body movement caused by something else. On a much larger group, the second input is not a discrete device at all — it is wheel speed information produced by the anti-lock braking system and shared with the engine controller over the vehicle network. Rapid, correlated variation across the wheels is a reliable proxy for a broken road surface, and using data the vehicle already generates is cheaper than fitting another sensor.
If this vehicle uses the second architecture, then P0319 is a data and network fault wearing the costume of a sensor fault. The repair lives in the brake control module, its wheel speed sensors, or the bus between it and the engine controller — and every minute spent looking for a second accelerometer under the car is wasted. The way to settle it is to scan all modules rather than the engine controller alone. A brake control module carrying its own wheel speed codes, or one that will not respond at all, answers the question immediately.
The pattern of codes is informative in a second way. P0319 stored on its own, with no P0318 alongside it, points away from anything the two channels share — the reference voltage, the ground and the controller's input stage are all evidently working for channel A. P0318 and P0319 stored together points back at exactly those shared elements, or at the controller. And either of them stored alongside P0317 shifts suspicion toward configuration, because a module told to expect content the vehicle does not have will complain about the channels as well as the hardware.
As with the rest of this small group of codes, nothing about engine operation changes. The cost is diagnostic capability: with a rough road input invalid, misfire monitoring is inhibited or suspended, the misfire readiness monitor will not complete, and a genuine misfire may pass unrecorded.
Common causes
- Wheel speed sensor fault causing the brake control module to stop supplying valid road roughness data
- Brake or ABS control module offline, unpowered or carrying its own stored faults
- Network wiring fault between the brake control module and the engine controller
- Engine controller configured for content this vehicle does not have, so a second channel is expected that never existed
- Second rough road accelerometer failed, disconnected or unsecured where one is genuinely fitted
- Open, short or high resistance in the second channel's signal wire
- Corroded connector on the second sensor or at an intermediate chassis connector
- Aftermarket wheel or tyre sizes distorting wheel speed data beyond the module's expectations
Symptoms
- Check engine light on with normal engine operation
- ABS or traction control warning lights present at the same time in the network-fault cases
- Misfire readiness monitor never completes
- Audible misfire with no misfire code recorded
- Emissions inspection failure on readiness
- Code returning after clearing without any obvious trigger
Diagnostic steps
- 1.Determine the architecture first. Manufacturer service information will say whether the second rough road input is a physical sensor or a network value from the brake control module, and nothing else should be attempted until that is known.
- 2.Scan every module on the vehicle rather than the engine controller alone. Wheel speed or brake system codes stored elsewhere are very often the whole explanation.
- 3.Note whether P0318 is stored alongside this code. P0319 alone exonerates the shared reference, ground and controller input; the pair together implicates exactly those.
- 4.Check for P0317 as well. Configuration codes and channel codes appearing together point at a module programmed for the wrong vehicle content rather than at a broken circuit.
- 5.On network-based applications, verify the brake control module is communicating and compare live wheel speed values across all four wheels at a steady road speed. One reading that lags or drops out is the fault.
- 6.On applications with a genuine second sensor, inspect its mounting, connector and harness routing, and compare its live value against the first sensor while the suspension is worked.
- 7.After repair, clear the codes and confirm the misfire readiness monitor completes on a normal drive cycle rather than assuming the light staying off is proof.
Repair cost
$100 – $1,200
The range is wide because the two architectures have different price structures. Diagnosis is $100 to $200 and is worth paying for here, since identifying which architecture the vehicle uses is most of the work. A wheel speed sensor is $180 to $400 fitted. Network or harness repair between modules is $150 to $500 depending on where the fault sits. A second rough road sensor, where one exists, is around $200 to $450 installed. A brake control module replacement with programming is the expensive tail at $700 to $1,200 and up, and should never be the first thing tried.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with wheel speed sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.