Code
P1238
FORD
P — Powertrain
Fuel Pump Secondary Circuit Fault
AI status
Completed
Completed
100%
Causes
- Blown fuse or faulty fuel pump relay
- Open or shorted wiring in the fuel pump secondary feed or ground
- Corroded or loose connector at the fuel pump module or in-line connector
- Failed fuel pump motor (internal short or open)
- Faulty fuel pump driver/module or PCM power transistor
- Water intrusion or contamination at the pump electrical connector
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- No-start or extended crank (engine cranks but won’t run)
- Intermittent stalling or loss of power
- Fuel pump does not prime when key is cycled
- Unusual battery drain or blown fuses on pump circuit
- Possible abnormal fuel pressure (low or dropping pressure)
What to check
- Read and record all stored and pending codes, freeze frame and live data with a capable scan tool
- Visually inspect fuses, relays, and in-line connectors for damage or corrosion
- Listen for fuel pump prime when key is turned to ON (audible hum at tank)
- Check fuel pressure with a gauge (compare to spec / expected pressure during key on and cranking)
- Measure voltage at fuel pump connector with key ON (test both supply and ground)
- Perform continuity/resistance checks on wiring between relay/fuse/PCM and pump
Signal parameters
- Battery feed to pump: approximately 11–14 V with key ON/engine running
- Pump ground/control: typically switched ground or PWM from pump driver — may show ground switching or a PWM waveform (frequency depends on module)
- Pump current draw: commonly in the 5–15 A range under load (varies by vehicle and pump)
- Voltage drop under load: should not fall below ~9–10 V at the pump during cranking/running (excessive drop indicates wiring/resistance issue)
- Relay coil feed: battery voltage on one terminal when key ON, control side pulled to ground by PCM or relay driver as designed
Diagnostic algorithm
- Retrieve codes and freeze frame, note conditions when P1238 set. Clear codes and attempt to re-create.
- Visually inspect fuses, fuel pump relay, connectors (pump module, in-line splice), and wiring for obvious damage or corrosion.
- With a DVOM measure battery voltage at the pump positive terminal with key ON and while cranking. Confirm consistent battery voltage feed.
- Check pump ground continuity back to chassis ground and PCM ground; measure voltage drop between pump negative and battery negative while pump runs.
- Backprobe relay output or pump connector to confirm relay/driver is commanding power. If control is PWM, capture waveform with scope or oscilliscope-capable scan tool.
- Measure pump current draw with a clamp meter while running. Compare to expected range; high current suggests pump internal fault or short, low/no current suggests open circuit or relay/fuse failure.
- If wiring and connectors test good, bench-test or temporarily apply fused battery power to the pump to verify operation (observe current and pressure).
- Inspect tank access (service cover) and connector pins for corrosion; repair or replace as needed. Repair any damaged wiring using OEM repair methods (splice blocks, solderless connectors per service manual).
- If wiring, relay, fuse, and pump bench test OK, suspect pump driver/module or PCM. Confirm using manufacturer-specific diagnostics and substitute known-good module if available before replacing PCM.
- After repairs, clear codes and perform road test to verify fault does not return and fuel pressure remains within specification.
Likely causes
- Blown fuse or poor/loose relay contacts
- Corroded connector or poor ground at the fuel pump module
- Damaged wiring or harness in tank-to-chassis run
- Worn or failed fuel pump motor drawing excessive current
- Faulty fuel pump driver/module (mounted near pump or in underbody fuse/relay pack)
Fault status
Status
P1238 — Fuel Pump Secondary Circuit Fault (Ford). The PCM detected an abnormal condition in the fuel pump secondary circuit (open, short, overcurrent, or driver fault). Investigation of fuses, relay, wiring, pump module and driver is required; do not assume final diagnosis without testing.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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