P1238

Fuel Pump Driver Module Off Line

Powertrain Fuel and Air Metering Fuel pump control 🟡 Moderate — Fix within a week ⚠️ Drive with Care
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What This Actually Means

In plain language — no jargon

The fuel pump driver module, which is like the relay controlling power to your fuel pump, has gone offline or failed to communicate. The ECU can't command the fuel pump to run, so fuel won't reach the engine.

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Symptoms You May Notice

3 known symptoms for this code
Engine cranks but won't start or run
No fuel pressure detected at the fuel rail
Check Engine Light illuminated
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECM monitors feedback signals from the fuel pump driver module to verify it's receiving and executing fuel pump commands. It checks for communication handshakes and voltage control signals. If the module fails to respond or confirm fuel pump activation within expected timeframes, a fault is logged.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Fuel pump driver response time Module acknowledges command within 10-50ms No acknowledgment or timeout >100ms
Driver module voltage output 12V+ to fuel pump relay coil when commanded <5V or 0V during activation request
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Fuel pump relay
Locate and swap the fuel pump relay with an identical relay from another circuit; if the code clears, the relay was faulty.
2
Fuel pump driver module wiring and connectors
Inspect and reseat all connections to the fuel pump driver module, cleaning corrosion from pins with electrical contact cleaner.
3
Fuel pump driver module
If wiring and relay test okay, the driver module itself has likely failed and requires replacement.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1238 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code P1238

What happens after you fix the fault

Once the fault is repaired, P1238 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.