Code
P1233
LINCOLN
P — Powertrain
Fuel Pump Driver Module Off-Line
Views:
UK: 32
EN: 61
RU: 41
AI status
Completed
Completed
100%
Causes
- Blown fuse or faulty fuel pump relay supplying FPDM
- Poor battery voltage or weak battery
- Damaged, corroded or disconnected FPDM connector or wiring
- Open/short on the vehicle communication bus (CAN) or missing termination
- Faulty FPDM (internal failure)
- PCM or other network module fault
Symptoms
- No fuel pump operation or intermittent pump operation
- Malfunction Indicator Lamp (MIL) illuminated
- Hard starting or no-start condition
- Stored communication-related trouble codes
- Possible reduced engine performance or stalling
What to check
- Query PCM with a capable scan tool: confirm P1233 and check freeze frame and related codes
- Record battery voltage with ignition ON and engine cranking
- Visually inspect FPDM connector, wiring, and fuel pump harness for damage or corrosion
- Check relevant fuses and fuel pump relay for continuity and proper operation
- Backprobe FPDM power and ground pins for battery voltage and good ground
- Check CAN bus signals at FPDM connector (CANH/CANL) and verify proper termination/resistance
Signal parameters
- Battery supply to FPDM: approximately vehicle battery voltage (key ON, ~12 V)
- Ground continuity: near 0 ohms to chassis ground
- CAN bus idle voltages: CANH and CANL near nominal bus idle (roughly mid-rail ~2.5 V each; differential ~0 V idle) — observe expected CANH/CANL voltages per factory data
- CAN bus termination resistance: approximately 60 ohms across CANH and CANL (two 120 Ω terminators in parallel)
- No meaningful periodic FPDM network messages present when module is off-line
Diagnostic algorithm
- Connect a scan tool, confirm P1233 and note any related codes (U-codes, fuel pump circuit codes). Record freeze-frame and symptom details.
- Verify battery voltage (>=12 V) with ignition ON and during cranking. Charge or replace battery if voltage is low.
- Inspect fuses and fuel pump relay; test for continuity and correct voltage at relay/fuse terminals. Replace faulty components.
- Visually inspect FPDM connector and wiring at the module and along the harness to the PCM for damage, corrosion, or rodent chew. Repair as needed.
- Backprobe FPDM power and ground pins: confirm constant battery voltage on the power pin (key ON) and good ground. Repair wiring if power/ground missing.
- Check CAN bus communication at the FPDM connector with a DMM/oscilloscope: verify CANH/CANL nominal voltages and presence of high-speed data when other modules are active. Measure termination resistance (~60 ohms).
- If CAN signals are absent at FPDM but present at PCM, trace/repair open or shorted CAN wiring between FPDM and network.
- If wiring, power, ground and CAN are good but module does not respond, consult factory procedures for FPDM module programming/replacement. Replace FPDM if directed and reprogram/relearn per manufacturer instructions.
- After repairs, clear codes, perform functional tests (fuel pump command, pressure tests) and road test. Re-scan to confirm code does not return.
Likely causes
- Connector at FPDM is corroded, loose or has bent pins
- Power or ground to the FPDM is lost (fuse, relay, wiring)
- Broken or shorted CANH/CANL wires between FPDM and PCM
- FPDM internal failure preventing network responses
Fault status
Status
Fuel Pump Driver Module off-line — no communication with PCM / network
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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