Code
P1189
LINCOLN
P — Powertrain
Pump Speed Signal Fault
Views:
UK: 29
EN: 63
RU: 32
AI status
Completed
Completed
100%
Causes
- Open/short or high resistance in pump speed sensor wiring
- Corroded/loose connector or poor ground at sensor or ECM
- Failed pump speed sensor (Hall, magnetic pickup, or optical sensor)
- Failed pump control module or ECM input circuit
- Mechanical pump failure (no rotation) or missing tone ring/reluctor
- Low system voltage or intermittent power supply to sensor
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced engine power or limp-in mode
- Hard start, no start, or intermittent stalling
- Poor fuel pressure or fuel delivery symptoms (if fuel pump related)
- Abnormal pump noise or no audible pump operation
- Related codes for fuel system, voltage, or speed sensors
What to check
- Read stored freeze‑frame data and all related DTCs; note operating conditions when code set
- Confirm exact pump and sensor location from vehicle-specific service information
- Visually inspect connectors and wiring for damage, corrosion, bent pins, or water intrusion
- Check battery/charging system voltage and grounds
- Backprobe sensor connector and verify reference power, ground, and signal with a multimeter
- Capture signal waveform with an oscilloscope or frequency meter while cranking and running
Signal parameters
- Sensor type: typically Hall-effect or magnetic pickup; outputs a square wave or AC pulse
- Voltage: sensor signal generally switches between ~0 V and reference (commonly 5 V); some systems use 0–12 V
- Frequency/duty: proportional to pump rotational speed — low frequency at idle, higher under load (tens to thousands of Hz depending on pump design)
- Reference: stable 5 V reference (verify) and a good chassis/signal ground
- Expected behavior: consistent, repeatable waveform with RPM; no intermittent dropouts or noise
Diagnostic algorithm
- Retrieve all codes and freeze frame data; check manufacturer TSBs for P1189 or related bulletin info.
- Identify which pump and sensor the ECM monitors (consult vehicle service manual).
- Visually inspect connectors, wiring harness and connector seals at the pump and ECM for damage or corrosion.
- With key ON engine OFF, backprobe the sensor connector: verify reference voltage (typically 5 V), ground continuity, and sensor supply.
- Start engine (or crank as required) and measure the sensor signal: use a scope to view waveform or use a frequency meter to confirm pulses proportional to engine speed.
- Perform a wiggle test on the harness while monitoring the signal to find intermittent faults.
- If no signal is present but reference and ground are good, check continuity from sensor connector to ECM pin; repair any opens/shorts.
- If wiring and connector are good but signal is incorrect, replace the pump speed sensor and retest.
- If a known-good sensor still fails or wiring/connector tests good, check/replace the pump control module or perform ECM input diagnostics per manufacturer procedures.
- After repairs, clear codes and perform test drive to confirm no recurrence and proper fuel/engine operation.
Likely causes
- Damaged or corroded connector at the pump speed sensor
- Failed pump speed sensor
- Broken/disconnected wiring between sensor and ECM
- Faulty pump control/driver module
- Mechanical seizure or internal pump failure preventing rotation
Fault status
Status
MIL ON — DTC P1189 stored. Freeze frame and operational data recorded at time of fault. Code may be intermittent; verify with live data and waveform capture before replacing components.
Repair difficulty: Medium
Diagnostic time: 1.0 to 3.0 hours
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