Diesel Trouble Codes

P1662 — IDM EN Circuit Failure — 7.3 Power Stroke

IDM EN Circuit Failure

Updated October 15, 2026

What it means

Ford enhanced code for a fault in the IDM enable (IDM EN) circuit between the PCM and the injector driver module. On the 7.3L Power Stroke the IDM drives the HEUI injectors and the enable line must be present for the IDM to operate; loss of enable can cause a crank-no-start and often appears with P1660/P1663.1

Most likely causes

  1. IDM enable (EN) wire open or short between PCM and IDM — The enable signal from the PCM to the IDM is interrupted or shorted, preventing the IDM from being commanded on. Inspect the PCM-to-IDM harness for chafing, corrosion, or pin damage at both connectors.1
  2. IDM power or ground fault — Loss of battery power or ground to the IDM can cause the enable circuit to read incorrectly and trigger P1662, often together with P1660/P1663. Verify IDM power/ground integrity and connections.12
  3. Faulty IDM connector or internal IDM failure — Corrosion, moisture, or internal failure of the IDM can disrupt the EN circuit and related IDM-to-PCM communications. Check IDM connectors and consider IDM health when P1662 appears with P1660/P1663.12
  4. PCM-to-IDM wiring/connector issue affecting IDM communications — The PCM-to-IDM harness carries enable, OCC, and FDCS signals; damage to this wiring can set P1662 and often co-occurs with P1660/P1663. Inspect the harness and pins for damage.123

How to diagnose

  1. Verify the code is present on a 1999–2003 7.3L Power Stroke and note any accompanying codes such as P1660 or P1663, which commonly appear with P1662.
  2. Inspect the IDM (driver-side fender) power and ground connections for corrosion, loose terminals, or damaged wiring; poor power/ground can cause enable circuit faults.
  3. Examine the PCM-to-IDM harness and connectors for chafing, moisture, or bent pins, focusing on the IDM enable (EN) wire and related IDM communication circuits.
  4. Check IDM connector condition for oil intrusion or corrosion and confirm secure seating; intermittent enable faults often trace to connector issues.
  5. If wiring and connections test good, evaluate IDM health in context of co-occurring IDM codes (P1660/P1663) before considering PCM involvement, as the enable circuit fault can stem from the IDM or its wiring.

Specs and test values

CheckNormal readingWhen to measureSource
Battery and charging voltage12.6–12.7 V at rest when fully charged; about 13.5 V runningEngine off, then running with loads onDieselHub

Parts and tools you may need

Tools you’ll need

Rough cost and difficulty

Likely repairPartsShop laborWho usually does it
Wiring or connector repair$10–$1001–4 hrsDIY with tools and a manual
Battery or charging-system repair$150–$5000.5–2 hrsEasy DIY
IDM (injector driver module), reman$330–$6001–2 hrsDIY with tools and a manual

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the truck is crank-no-start, shows multiple IDM codes, or wiring tests inconclusive, have a qualified diesel technician perform pinpoint electrical tests and, if needed, IDM/PCM evaluation. Do not attempt high-pressure oil or injector repairs without proper training and safety equipment.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources

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

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

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