5 HARD START AND NO START DIAGNOSTICS 177
12. Main Power Relay to IDM
Figure 207
Purpose
To determine correct power supplied to operate the
IDM
The IDM requires 7 V minimum for correct operation.
Voltage Measurement at 12–Pin Connection with
Breakout Harness
Tools
• 12-Pin Breakout Harness
• Digital Multimeter (DMM)
Procedure
WARNING: To avoid serious personal injury,
possible death, or damage to the engine or
vehicle, read all safety instructi on s in the “Safety
Information” section of this manual.
NOTE: Batteries must be fully charged before doing
the following steps.
1. Turn the ignition switch to OFF and ensure all
accessories turned off.
2. Disconnect 12-pin c onnector above the ECM and
IDM.
CAUTION: When disconnecting the 12-pin connector,
the lock can come loose. Put the lock back in the
correct place before reconnecting the connector.
Figure 208 12-pin Engine Harness Connector
3. Connect 12-pin Breakout Harness between both
engine and chassis c onnectors.
4. Connect leads of the DMM to each of the following
test points:
• POS 12 to NEG 1 (IDM PWR to IDM GND)
• POS9toNEG1(V
IGN
to IDM GND)
• POS9toNEG8(V
IGN
to MPR)
• POS6toNEG1(IDMLogicPWRtoIDM
GND)
5. Crank engine for 20 seconds and measure
voltage.
6. Record the lowest voltage on Diagnostic Form.
• If the voltage is below 7 V, the IDM m ain
power relay may be resetting, resulting from
low voltage and current from the batteries
or problems in the ignition circuit or power
feed circuits. See “IDM PWR, Injector Drive
Module Power” (page 479) in Section 7.
• If the voltage is above 7 V, c ontinue with Hard
Start And No Start diagnostic tests.
NOTE: Results can be above 7 V, but there
may be a problem between the 12-pin connector
and the IDM. If a Hard Start / No Start problem
remains after all Diagnostic Form te sts are
complete, check voltage at IDM connector.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
©August 2008 Navistar, Inc.
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