Damaged or corroded wiring harness between the PCM and the injector driver module, especially at connectors; Failed injector driver module (IDM) or its internal enable circuit; Blown fuse or poor ground connection feeding the IDM circuit; Faulty PCM driver stage for the IDM_EN output; Water intrusion or chafing in the harness near the engine valley or firewall; Loose or backed-out terminal pins at the PCM or IDM connectors

DTC codes / Ford codes / P1662

P1662 · FordIDM_EN Circuit Failure

Q: What does code P1662 mean?

IDM_EN Circuit Failure. P1662 on Ford vehicles indicates that the Powertrain Control Module (PCM) has detected a failure in the Injector Driver Module Enable (IDM_EN) circuit, which is the signal path that allows the injector driver module to power the fuel injectors. The PCM monitors this circuit for expected voltage changes and sets the code when the signal is missing, shorted, or out of range, meaning the engine may not receive proper fueling commands.

P1662 on Ford vehicles indicates that the Powertrain Control Module (PCM) has detected a failure in the Injector Driver Module Enable (IDM_EN) circuit, which is the signal path that allows the injector driver module to power the fuel injectors. The PCM monitors this circuit for expected voltage changes and sets the code when the signal is missing, shorted, or out of range, meaning the engine may not receive proper fueling commands.

SystemPowertrain

Code typeFord specific

SeverityHigh

Fix difficultyProfessional

AreaComputer and output circuits

Symptoms you may notice

Engine cranks but does not start or starts then stalls immediately
Rough running or misfire under load, sometimes with a flashing check engine light
Reduced engine power or limp mode with the throttle unresponsive
Often no symptoms besides the warning light if the fault is intermittent
Hard starting when cold or after sitting, requiring long cranking
Poor fuel economy or rich-running smell from the exhaust

Common causes, most likely first

Damaged or corroded wiring harness between the PCM and the injector driver module, especially at connectors
Failed injector driver module (IDM) or its internal enable circuit
Blown fuse or poor ground connection feeding the IDM circuit
Faulty PCM driver stage for the IDM_EN output
Water intrusion or chafing in the harness near the engine valley or firewall
Loose or backed-out terminal pins at the PCM or IDM connectors

How to diagnose and fix it

Check all fuses and grounds related to the injector driver module and PCM, then clear the code and retest
Inspect the IDM_EN wire from PCM to IDM for continuity, shorts to ground, and shorts to power with a multimeter
Wiggle-test the harness and connectors while watching live data for the IDM_EN signal to catch intermittent faults
Substitute a known-good injector driver module and retest to rule out the module itself
Verify PCM output on the IDM_EN pin with a scope or bidirectional scan tool; if the PCM cannot command the circuit, diagnose the PCM
Repair or replace damaged harness sections and terminals, then perform a full drive cycle to confirm the code stays cleared

What the IDM_EN code really tells you

A P1662 does not automatically mean the injector driver module is bad; chafed wiring in the engine valley is a very common cause on Ford trucks and vans.
The PCM may set this code only after the engine has run for a specific time or under certain load conditions, so a simple key-on test can miss an intermittent fault.
A weak battery or poor ground can cause the IDM_EN circuit to drop out momentarily, setting the code without any hard failure.
Some scan tools show IDM_EN as a status parameter; watching it while cranking or wiggling the harness is faster than static resistance checks.
Replacing the PCM without first proving the IDM_EN output is faulty is a costly misdiagnosis trap, because the circuit wiring and module are far more likely to fail.

Can I keep driving with P1662?

Do not continue driving with P1662 because the engine may stall without warning or fail to restart, leaving you stranded or in a dangerous position. If the vehicle is already running poorly, park it safely and arrange a tow rather than risk a sudden loss of power.

Tools that help

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Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.