GB Tech
Bulletin #103: Ford Injector Driver Module (IDM) Replacement
The IDM module can fail as
a result of an internal failure or be damaged by other
malfunctioning components on the vehicle. In order to assist in the
diagnosis of the IDM module and ensure the replacement module is not
damaged when installed, the following tests and procedures should be
performed.
Injector Resistance and Wiring Tests
The IDM module can
fail as a result of an internal failure or be damaged by other
malfunctioning components on the vehicle. In order to assist in the
diagnosis of the IDM module and ensure the replacement module is not
damaged when installed, the following tests and procedures should be
performed.A
common failure found on the Powerstroke 7.3L injection system is
faulty electrical wiring between the IDM module and the fuel
injectors. The wiring passes through connectors which are molded
into the valve cover gaskets (see illustrations 1 and 2). The
following test ensures the wiring between the IDM module and
injectors are within specification. This procedure will also test
for defective injector solenoid(s). By measuring the resistance
(ohms) between each injector’s power-feed and ground circuit, the
total circuit and wiring resistance can be verified. This ensures
that there are no shorted or open circuits to the injectors.
TESTING PROCEDURE
The following tests should be
performed with the key off, the IDM harness disconnected
from the module and all other harness connectors plugged
in (connectors to valve covers, etc.). Measurements are taken by probing
the female terminals from the connector face
(where it would normally plug into the IDM module).
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TEST 1: Use an multi-meter to measure the
resistance between each power feed and each
injector’s ground circuit at the IDM harness
connector. There is one power feed for each
cylinder bank.
TEST 2: Measure the resistance
between each power feed and ground. This should indicate
an open circuit. If resistance is present check for
damaged valve cover gasket connectors and the wiring
beneath the valve cover gaskets (see below for illustrations).
TEST 3: Check for damaged injector wiring
harness; Measure the resistance between the
each
injector power feed and the ground shield for the
injector wires.
WARNING: The wires to the
injectors are
shielded wire, DO NOT pierce
injector wires,
doing so will permanently damage
the
harness.
Nominal solenoid resistance
for Powerstroke
injectors is 2.9 Ohms. This test
measures entire circuit resistance which includes
wire and valve cover connector resistance. All
readings for the vehicle should be consistent
between each circuit. This test checks for
injector circuits that are shorted to ground, which will
cause immediate and permanent damage to the IDM module.
The resistance between these pins should be open
(infinity), indicating no path to ground. This should
indicate an open circuit. If resistance is present
inspect the wiring harness for damage.
NOTE: Always consult vehicle
specific service and diagnostic information. |
Visual Inspection - Wiring Harness &
Connectors
Inspect
the connectors at the valve cover gaskets for damage and
proper fit. Over time the connectors can become brittle and
crack. Wiggling the connectors while performing the tests on
the previous page can help detect intermittent connections.
If the electrical tests on the previous page indicate there
is a problem remove the valve cover and inspect the Injector
harnesses.
Illustration 1
1994-1998 Valve Cover Gasket &
Injector Harness Detail
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Illustration 2
1999-2003 Valve Cover Gasket &
Injector Harness Detail |
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