What it means
Same as P0652 on reference rail C. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Reference rail C supplies a shared reference signal to sensors monitored by the powertrain control module. P0698 sets when the module detects that rail C is below its expected range, commonly because the rail is pulled toward ground or has excessive resistance at a connection.
Common causes
Most likely first.
- Reference rail shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Record freeze-frame data and scan for related sensor or module codes to identify what else lost its rail C reference.
- With the ignition off, inspect rail C wiring and connectors for chafing, moisture, corrosion, or pushed-back pins.
- Use live data while gently moving the accessible rail C harness to see whether the fault or affected sensor readings change.
- Following the wiring information for the vehicle, disconnect rail C sensor branches one at a time and check whether the low condition clears.
- Measure the rail C circuit and its connected components for a short to ground or excessive resistance, comparing results with the manufacturer's specification.
Common fixes
- Repair chafed rail C wiring and secure it away from rubbing points.
- Clean or repair corroded connectors and restore loose or pushed-back terminals.
- Replace a sensor on rail C if testing confirms it is pulling the shared reference low.
- Clear codes and perform any required sensor or module relearn after the circuit is repaired.
Can I keep driving?
The engine may enter limp mode, stall, or fail to start if rail C supports critical sensors. Avoid relying on the vehicle until the related faults are understood; continued driving may cause unpredictable operation.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.