P1684

Code

Generic P — Powertrain

Metering Oil Pump Position Sensor Circuit Malfunction

Brand: Generic

Type: P — Powertrain

Views: UK: 47 EN: 77 RU: 47

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Causes

Faulty metering oil pump position sensor
Open, shorted or damaged wiring harness to the sensor
Corroded or loose connector pins
Poor sensor ground or reference voltage
Metering oil pump mechanical failure or seizure
ECM internal fault or poor ECM connector contact

Symptoms

MIL (check engine light) illuminated
Stored P1684 or related fault codes
Possible reduced engine power or limp-home mode
Abnormal oil metering behaviour (low or erratic oil delivery)
Unusual engine noise if oiling is affected
Difficulty starting or rough running if ECM limits operation

What to check

Read and record stored/pendant DTCs and freeze-frame data with a scan tool
Visually inspect sensor, connector, and wiring harness for damage or corrosion
Check battery and charging voltage (low voltage can cause false codes)
Backprobe sensor connector and confirm reference voltage, signal voltage and ground
Wiggle test wiring while monitoring live data for intermittent faults
Check continuity and resistance of sensor wiring to the ECM with ignition off

Signal parameters

Reference voltage: typically ~5.0 V (±0.5 V) from ECM
Sensor signal voltage: typically 0.2–4.8 V depending on position (varies by design)
Ground continuity:
Open-circuit detection: infinite or very high resistance when sensor unplugged
Pulse or frequency-type sensors: frequency or duty cycle should change smoothly with pump movement

Diagnostic algorithm

Verify customer complaint and confirm MIL is on. Connect scan tool, read P1684 and any related codes; note freeze-frame and live data for the MOP position sensor.
Clear codes and attempt to re-create. If P1684 returns, proceed with wiring and sensor checks.
Visually inspect the sensor, connector, and harness for damage, corrosion, or poor routing near heat or moving parts.
With ignition ON (engine off), backprobe the sensor connector: verify reference voltage from ECM (~5 V), good ground, and a stable signal reference. Compare to expected ranges in signal_params.
If reference or ground incorrect, trace wiring back to ECM; repair open or corroded connections, repair grounds.
If reference and ground are good but signal is out of range or intermittent, perform continuity/resistance check of signal wire to the ECM with ignition off. Repair any broken wiring.
Wiggle harness and connectors while watching live data for intermittent changes. Repair or secure harness as needed.
If wiring tests good, measure sensor output while operating the pump (cranking or running as safe) and confirm signal changes smoothly with pump movement. Replace sensor if output is incorrect or noisy.
Inspect metering oil pump mechanically — check for binding, abnormal resistance, or internal damage that could prevent correct sensor movement. Repair or replace pump if needed.
If sensor and pump are confirmed good, consider ECM connector issues or ECM fault. Perform ECM input diagnostics or replacement only after verifying wiring and components.
After repairs, clear codes, perform any required relearn or calibration procedures for the metering oil pump position sensor, then road test and re-scan to confirm repair.