Diesel Trouble Codes

P1660 — Fuel Injection Pump Control Module (7.3 Power Stroke)

P1660 is a Ford-enhanced code that the PCM has detected a malfunction in the fuel injection pump control module or its communication circuit. On the 1999–2003…

Updated September 2, 2026

What it means

The PCM reports a fault in the fuel injection pump control module communication/circuit. On the 7.3L Power Stroke the injector driver module (IDM) is the module that drives the HEUI injectors, and P1660 is an IDM/output-circuit fault. The engine uses HEUI injection with a high-pressure oil pump; there is no common rail or high-pressure fuel pump.12

Most likely causes

  1. IDM power/ground or internal IDM failure — The IDM is mounted on the driver-side fender and powers the eight HEUI injectors. Loss of power, ground, or internal failure can set P1660. Typical on this platform: 7.3L Power Stroke — HEUI, IDM/output-circuit faults P1660, P1662, P1663.1
  2. Chafed or corroded IDM wiring/harness — Wiring between the PCM and IDM, or the IDM connectors, can be damaged by heat/vibration. The generic definition is a malfunction in the fuel injection pump control module or its communication circuit.1
  3. Under-Valve-Cover Harness (UVCH) degradation affecting injector circuits — Oil-soaked, chafed UVCHs are a known failure point and can cause injector and glow-plug circuit codes. While P1660 is an IDM/output fault, degraded UVCHs contribute to injector circuit issues on this platform.1
  4. PCM power/ground or internal PCM fault — PCM internal KAM/ROM errors are common on this platform and often relate to PCM power/ground issues. P0603/P0605 are typical PCM internal faults.1

How to diagnose

  1. Verify code and freeze-frame; confirm P1660 is present and note accompanying codes such as P1662/P1663 or injector circuit codes.
  2. Inspect IDM power and ground circuits and connectors for corrosion, loose pins, or heat damage; check IDM fuse/relay per wiring diagram.
  3. Perform a visual and wiggle test of the PCM-to-IDM harness for chafing, oil contamination, or damaged insulation.
  4. Check IDM connector pin tension and clean as needed; measure IDM supply voltage with key on.
  5. Inspect both Under-Valve-Cover Harnesses for oil saturation, chafing, and connector integrity; look for signs of injector circuit faults.
  6. Review recent repairs or moisture exposure that could affect PCM/IDM grounds.
  7. If no wiring faults are found, consider IDM functionality and PCM communication integrity; compare with known-good values.
  8. Clear codes, test drive, and re-scan to confirm P1660 returns.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and vehicle condition. IDM replacement, harness repair, or PCM service can be costly; diagnosis should confirm the root cause before replacing modules.

When to see a pro

If the IDM or PCM needs replacement or programming, or if high-pressure oil/fuel system work is required, have a qualified diesel technician perform the work. Do not attempt repairs to safety-critical high-pressure systems without proper training and tools.

Sources

  1. Curated DTC seed — 7.3 Power Stroke (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 7.3 Power Stroke (curated) ↩︎