P1238

Code

Other P — Powertrain

Fuel Pump Secondary Circuit Malfunction

Brand: Other

Type: P — Powertrain

Views: UK: 24 EN: 42 RU: 32

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Page language: EN

Causes

Blown fuse or faulty fuse link in the fuel pump secondary feed
Faulty fuel pump relay or control module
Open, short or high-resistance wiring in the secondary pump circuit (including damaged connector pins)
Corroded or loose ground connection for the pump or control module
Failed fuel pump motor or internal pump wiring
Faulty ECM/PCM or fuel pump control module (rare)

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Engine cranks but is hard to start or will not start
Intermittent stalling or loss of power under load
No or low fuel pressure at the rail
Fuel pump does not run or runs intermittently
Unusual electrical behavior (clicking relay, battery drain, blown fuses)

What to check

Read stored/active codes and freeze-frame data with a scan tool; note related codes and conditions
Verify battery voltage and state of charge before testing (low battery affects results)
Visually inspect fuses, relay(s) and fusible links for continuity and correct installation
Inspect harness and connectors at the fuel pump and pump relay/module for corrosion, bent pins, looseness or water intrusion
Check for relay operation (listen for click) when key is turned to ON and when cranking
Measure voltage at the fuel pump power terminal with key ON and while cranking

Signal parameters

Expected terminal voltage at pump: ~battery voltage (11.5–14.5 V) when pump commanded
Pump current draw (typical range): ~5–20 A depending on pump; compare to OEM spec
Resistance of pump motor winding: low ohms (typically
Control output from ECM/pump module: switched 0–12 V or PWM duty cycle when commanded (use scope or scan tool to verify)
Fuel pressure: refer to vehicle manufacturer specification (commonly ~30–60 psi for gasoline port-injected systems)

Diagnostic algorithm

Safety first: relieve fuel pressure if you will open the fuel system. Wear eye protection and work in a well-ventilated area.
Connect a scan tool, record freeze-frame and related codes, then clear codes and attempt to re-run to capture behavior.
With key ON (engine off), verify battery voltage at battery terminals. Note voltage for baseline tests.
Inspect fuses, fusible link(s) and pump relay; measure continuity and replace any blown components.
Locate the fuel pump connector and visually inspect for corrosion, water intrusion, bent pins or damaged insulation; repair as needed.
Backprobe the pump power and ground terminals. With key ON and while cranking (or when commanded by scan tool), measure voltage at the pump power terminal. If no voltage, trace back through relay and fuse.
If pump has battery voltage but does not run, measure current draw with a clamp meter during operation. Low/no current suggests open/worn pump; excessive current suggests internal short/dragging.
If no voltage at pump and relay does not click, test relay coil and control side. Verify the ECM/pump module control output using a voltmeter or scope. If ECM does not command when expected, look for input conditions that inhibit pump (immobilizer, crank signal, safety relays).
If control module output appears intermittent or abnormal, inspect wiring for short to voltage/ground and repair. Wiggle harness while monitoring voltage/current to find intermittent faults.
Perform a fuel pressure test at the rail while commanding the pump; compare to spec. Low pressure with correct pump voltage/current indicates pump or filter restriction.
Bench-test the pump (if removable) by applying correct voltage and observe current draw and flow. Replace pump if it fails bench test.
After repairs, clear codes and confirm repair with a road test and re-scan. If code returns, capture freeze-frame PIDs and proceed to module-level diagnostics or specialist support.

Likely causes

Damaged connector, pin corrosion or broken wire in the pump secondary wiring harness
Failed pump relay or pump control module
High-resistance/poor ground at pump or module
Worn or failed fuel pump motor causing overcurrent or open circuit
Blown fuse or fusible link supplying the secondary circuit

Fault status

⚠️ Status

Fuel pump secondary circuit malfunction detected — abnormal voltage, open, short or control signal detected on the secondary fuel pump circuit. May cause no/low fuel pressure or intermittent pump operation.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-4.0 hours

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P1238 — Fuel Pump Secondary Circuit Malfunction