Ford Power Stroke · Fuel Injector Cylinder 3High

Ford Power Stroke P0203: Injector Circuit Open — Cylinder 3

P-Code P0203 (FMI N/A) — Injector Circuit / Open - Cylinder 3

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Quick Answer

P0203 on your Ford Power Stroke means the injector circuit for cylinder 3 has an open condition — no current flow to fire the injector. On 6.0L trucks check FICM voltage and the under-valve-cover harness before pulling the injector.

Overview: Ford Power Stroke P-Code P0203

P0203 is a high-severity code because cylinder 3 isn't firing, which means rough running, misfires, and the risk of unburned fuel entering the aftertreatment system. ProfessionalDieselRepair.com measures the full electrical path — injector resistance, harness continuity, and FICM voltage on 6.0L trucks — before recommending any parts.

Repair Snapshot

Time

2 - 8 Hours

Difficulty

Advanced

Parts Cost

$300 - $1,500

Dealer Labor

$400 - $2,000

Tools Required

  • Diesel Laptops Scan Tool
  • Snap-on NEXIQ USB-Link
  • Multimeter

What P-Code P0203 Means

P0203 on the Ford Power Stroke means the injector driver circuit for cylinder 3 detected an open-circuit condition — either the wiring between the injector driver module and the cylinder 3 injector is broken, or the injector solenoid coil itself has failed open. On Power Stroke engines with an FICM (Fuel Injector Control Module) — particularly the 6.0L — a degraded FICM supply voltage can also produce individual injector open faults by failing to energize the circuit fully. This is a high-severity code: cylinder 3 will not fire, resulting in a significant misfire, rough running, and potential catalytic converter or DPF damage if continued. ProfessionalDieselRepair.com always measures injector circuit resistance and FICM voltage before condemning an injector.

Symptoms Drivers Notice

  • Rough idle with a noticeable miss
  • Check engine light on
  • Reduced power and potential smoke from an unfired cylinder
  • Possible DPF-related codes from unburned fuel entering the aftertreatment system
  • Engine knock or vibration at idle from the missing cylinder

Most Likely Root Causes

Failed injector solenoid coil (open winding)

Common

The injector solenoid coil develops an internal open circuit, preventing current flow through the energizing circuit regardless of commanded voltage.

Degraded under-valve-cover harness on 6.0L Power Stroke

Common

The 6.0L's under-valve-cover wiring harness is bathed in hot oil and heat, causing insulation to crack and break individual injector circuit conductors.

Degraded FICM with insufficient output voltage on 6.0L Power Stroke

Common

A 6.0L FICM that cannot build proper 48V injection voltage fails to energize injectors fully, setting individual open-circuit codes across multiple cylinders.

Damaged or disconnected injector harness connector

Occasional

A connector that wasn't fully seated after previous engine work, or a terminal that backed out from vibration, breaks the circuit to the injector.

Common Misdiagnoses (Don't Waste Parts)

Replacing the cylinder 3 injector as a parts-cannon first step without checking the under-valve-cover harness or FICM voltage

Why it happens: The code names the injector, so the injector gets swapped — but on the 6.0L Power Stroke the harness and FICM are both more common failure points than the injector itself for an open-circuit code.

Do this instead: Measure injector resistance, check harness continuity, and test FICM output voltage before ordering an injector. A $200 FICM rebuild is far cheaper than a set of replacement injectors.

Missing a second or third simultaneous injector code that suggests a module fault rather than individual injector failure

Why it happens: Technicians focus on the single code displayed without noting that two or three cylinder codes appeared together, which is a pattern-recognition flag for FICM or harness failure.

Do this instead: Pull all stored codes at once with Diesel Laptops or Snap-on NEXIQ and look for multiple simultaneous injector faults — two or more usually means FICM or harness rather than multiple individual injector failures.

Master Tech Commentary

Mechanic's Notes

Shop tip: ProfessionalDieselRepair.com always checks FICM voltage on 6.0L Power Strokes before condemning an injector for P0203 — a degraded FICM producing less than 45V will set multiple injector open-circuit codes even with perfectly good injectors. The under-valve-cover harness on the 6.0L is also a common culprit and should be inspected for heat-damaged insulation before pulling the injector. On 6.7L trucks without a FICM, resistance and harness continuity checks are the primary path. Use Diesel Laptops or Snap-on NEXIQ for a cylinder contribution test after repair to confirm the fix.

Step-by-Step Diagnostic Procedure

  1. Step 1: Connect Diesel Laptops or Snap-on NEXIQ and pull P0203 with associated codes. Note whether other individual injector codes are also present — multiple simultaneous injector codes often point to a module-level fault rather than individual injector failures.
  2. Step 2: With the engine off, unplug the cylinder 3 injector connector and measure injector solenoid resistance across the two terminals. Most Power Stroke injector solenoids should read approximately 0.2–2.0 ohms — an open reading (OL/infinite) confirms injector coil failure.
  3. Step 3: If injector resistance is within spec, use a multimeter to check continuity through the harness from the injector connector back to the FICM connector. An open reading in the harness confirms a wiring fault.
  4. Step 4: On 6.0L Power Strokes specifically, check FICM supply voltage at the FICM connector with the engine running — it should read approximately 48V. A degraded FICM that cannot build proper injection voltage will set individual open-circuit codes even with good injectors and wiring.
  5. Step 5: Inspect the injector wiring harness under the valve cover on 6.0L trucks — the under-valve-cover harness is a notorious failure point where insulation degrades from heat and oil contamination.
  6. Step 6: After any repair, clear codes with Diesel Laptops or Snap-on NEXIQ and run a contribution test to confirm cylinder 3 is contributing equally to engine output.

Professional service / OEM-level scan tools are recommended before clearing this fault for good.

Live Data & Freeze-Frame Tips

Run an injector contribution balance test using Diesel Laptops or Snap-on NEXIQ — a cylinder 3 contribution of zero or significantly less than other cylinders confirms it is not firing. On 6.0L trucks, also monitor FICM supply voltage under cranking and at idle — consistent reading below 45V warrants FICM testing.

Safety Warnings

  • On 6.0L Power Strokes, depressurize the high-pressure oil system before removing injectors — residual high-pressure oil can cause injury.
  • Allow the engine to cool before reaching into the valve cover area on any Power Stroke variant.

When to Limp In vs Tow

If the misfire is severe or accompanied by visible smoke, stop driving. Running a diesel long-term with a dead cylinder risks DPF damage from unburned fuel and can wash cylinder walls with raw diesel. Tow if you cannot promptly repair the fault.

Prevention Tips for Fleets & Owner-Operators

  • Service the FICM and inspect the under-valve-cover harness at high-mileage intervals on 6.0L Power Strokes.
  • Use quality diesel and avoid contaminated fuel — injector coil failures are accelerated by poor fuel lubricity.
  • Address oil leaks into the valve cover area promptly to reduce heat soak on the under-valve-cover harness.

Related Fault Codes

Frequently Asked Questions

Can I drive my Power Stroke with P0203?

Only briefly to get it to a shop. Running with a dead cylinder risks rough-running damage to motor mounts and causes unburned fuel to enter the DPF, which can ignite during a regen cycle. Get it diagnosed promptly.

How do I know if it's the FICM or the injector on my 6.0L?

Check FICM supply voltage first — it should read approximately 48V with the engine running. Then measure injector resistance with the engine off. A degraded FICM below 45V that's setting multiple injector codes is more likely the culprit than a simultaneous multi-injector failure.

What does P0203 mean specifically on the 6.7L Power Stroke?

On the 6.7L there is no separate FICM — the ECM directly controls injection. P0203 on a 6.7L points to a wiring harness fault or a failed injector solenoid. Measure resistance at the injector and continuity back to the ECM harness connector.

How much does a Power Stroke injector replacement cost?

A single new OEM-quality injector for a 6.0L or 6.7L Power Stroke typically runs $350–$600 in parts. Labor to replace one injector is roughly $300–$500 at an independent shop depending on accessibility. Under-valve-cover harness replacement on the 6.0L adds another $200–$400 in parts and labor.

Will P0203 cause my Power Stroke to go into limp mode?

Not typically from P0203 alone, but severe misfires can trigger a torque reduction strategy on some model years. Drivability will be noticeably rough and power will feel reduced even without a formal limp-mode flag.

Should all eight injectors be replaced at once on a high-mileage 6.0L?

It's worth discussing with your shop. If the truck has over 200K miles and one injector has failed, the others are likely not far behind. A set replacement is expensive upfront but can save significant repeated labor costs compared to doing them one at a time.