7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 447
IAH Pin-Point Diagnostics
Figure 455 IAH circuit diagram
Voltage Check at Element – Output State Test (Turn the ignition switch to ON. Run Glowplug / Inlet Air
Heater Output State Test. For help, see “Inlet A ir Heater Output State Test” in Section 3 (page 68).)
Test Point
Spec Comment
Element terminal 1 to gnd B+
If < B+, check relay and circuit for element 1. Do Voltage
Checks (page 449) and Harness Resistance Check (page
449).
If equal to B+, do Amperage Draw Check.
Element terminal 2 to gnd B+
If < B+, check relay and circuit for element 2. Do Voltage
Checks (page 449) and Harness Resistance Check (page
449).
If equal to B+, do Amperage Draw Check.
NOTE: When a single IAH circuit fails, suspect that circuit only. If both elements or circuits do not have voltage,
verify the ECM programming. If the ECM programming is correct, do Actuator Voltage Checks at ECM (page
449) , Harness Resistance Checks – Relay to ECM (page 450), and Harness Resistance C heck – R elay to
12–pin Connector (page 450).
Amperage Draw Check (Secure AMP Clamp around element feed wire. Turn the ignition switch to ON.
Run Glowplug / Inlet Air Heater Output State Test. For help, see “Inlet Air Heater Output State Test” in
Section 3 (page 68).)
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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