Nissan Titan XD · Fuel Injector Control Module RelayHigh

Nissan Titan XD P0612: Fuel Injector Control Module Relay Control

P-Code 0612 (FMI N/A) — Fuel Injector Control Module Relay Control

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Quick Answer

P0612 on the Nissan Titan XD means the FICM relay control circuit has a fault. Swap the relay, check its fuse, and verify power to the injector control module before replacing the FICM.

Overview: Nissan Titan XD P-Code 0612

P0612 on the Nissan Titan XD ISV5.0 indicates the ECM cannot properly control power to the fuel injector control module through its relay circuit. ProfessionalDieselRepair.com tests the FICM relay and fuse first on P0612 no-start calls — most failures are simple power delivery problems rather than a failed injector driver module.

Repair Snapshot

Time

30 Minutes - 2 Hours

Difficulty

Intermediate

Parts Cost

$15 - $600

Dealer Labor

$200 - $500

Tools Required

  • Cummins INSITE
  • Jaltest Diagnostic System
  • Multimeter
  • Relay Puller
  • Basic Fuse Kit

What P-Code 0612 Means

P0612 on the Nissan Titan XD with the Cummins ISV5.0 means the ECM has detected a fault in the fuel injector control module relay control circuit. The FICM relay supplies power to the injector driver module that operates the common-rail injectors. A failed relay, blown fuse, or open control wire can set P0612 and cause no-start or severe misfire conditions.

Symptoms Drivers Notice

  • Check engine light with possible no-start or rough running
  • FICM power relay may not click when key is cycled to on
  • Injector control module may show no communication in Cummins INSITE
  • Engine may crank normally but fail to fire if FICM power is absent
  • Possible companion codes related to injector circuit or FICM communication

Most Likely Root Causes

Failed FICM power relay

Very Common

Relay coil or contact failure prevents the ECM from switching power to the injector control module.

Blown fuse in the FICM relay supply circuit

Common

A short downstream or aged fuse opens the circuit, removing FICM power and setting P0612.

Open or corroded control wiring between ECM and relay

Moderate

Harness damage or corroded relay socket pins prevent reliable relay engagement.

Common Misdiagnoses (Don't Waste Parts)

Parts-cannon FICM replacement when the relay or fuse never supplied power

Why it happens: No-start with injector codes points attention to the FICM itself.

Do this instead: Swap the relay, verify the fuse, and measure voltage at the FICM power feed with key on before ordering a module.

Replacing injectors for a relay control electrical fault

Why it happens: Misfire or no-start symptoms are attributed to fuel injectors.

Do this instead: Confirm FICM power and communication in Cummins INSITE. Injectors cannot operate without a powered and communicating FICM.

Master Tech Commentary

Mechanic's Notes

Shop tip: ProfessionalDieselRepair.com swaps the FICM relay and checks its fuse before any FICM replacement on Titan XD P0612 calls. A $20 relay fix resolves most no-start cases — a parts-cannon FICM order is avoided when power never reached the module because of a blown fuse or corroded relay socket.

Step-by-Step Diagnostic Procedure

  1. Step 1: Scan with Cummins INSITE or Jaltest and confirm P0612 with any related FICM or injector codes.
  2. Step 2: Locate the FICM relay in the underhood fuse box. Swap with an identical relay to test quickly.
  3. Step 3: Check the fuse protecting the FICM relay circuit. Replace any blown fuse only after identifying why it failed.
  4. Step 4: With key on, verify battery voltage at the relay output terminal when the relay is commanded. No voltage indicates relay or control circuit failure.
  5. Step 5: Inspect wiring from the ECM to the relay and from the relay to the FICM for opens, corrosion, or damage. Repair harness faults before replacing the FICM.

Live Data & Freeze-Frame Tips

In Cummins INSITE or Jaltest, check FICM communication status and injector control power with key on and during crank. The FICM should come online within seconds of key-on. If communication is absent, measure relay output voltage at the FICM power feed to isolate relay and fuse faults from module failure.

Safety Warnings

  • Disconnect batteries before working on FICM connectors or high-pressure fuel components.
  • Do not bypass fuses with higher amperage ratings — find and repair the short that blew the original fuse.
  • Relieve fuel system pressure per service manual if fuel lines near the FICM are disturbed.

When to Limp In vs Tow

Tow if the Titan XD cranks but will not start and basic relay and fuse checks do not restore FICM power.

Prevention Tips for Fleets & Owner-Operators

  • Replace aging relays in the underhood fuse box during major service.
  • Inspect relay socket terminals for corrosion on high-mileage trucks.
  • Address water intrusion in the fuse box after cab washing or flood exposure.

Related Fault Codes

P0611

FICM performance fault — may follow if relay issues cause module power loss.

P0201

Injector circuit cylinder 1 — may set when FICM power is compromised.

P0562

System voltage low — weak batteries can prevent reliable relay operation.

Frequently Asked Questions

What does P0612 mean on a Nissan Titan XD?

P0612 means the ECM detected a fault in the fuel injector control module relay control circuit. The FICM may not receive power, causing no-start or misfire conditions.

Where is the FICM relay on the Titan XD?

The FICM power relay is in the underhood fuse and relay box. Consult the lid diagram or service manual for the exact location on your model year.

Can a bad relay cause a no-start?

Yes. Without relay power, the FICM cannot drive the injectors and the engine will crank without firing even with good fuel pressure.

Should I replace the FICM for P0612?

Not until the relay, fuse, and power feed are verified. Most P0612 cases resolve with relay or wiring repair rather than FICM replacement.

Which tools diagnose P0612 on the Titan XD?

Cummins INSITE shows FICM communication and injector control status. Jaltest also supports power circuit testing and fault clearing on ISV5.0 trucks.

How much does P0612 repair cost?

A relay or fuse repair may cost under $50. FICM replacement, if actually required, can run $400-$800 plus labor. Relay diagnosis first avoids unnecessary module expense.

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