7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 449
HarnessResistanceCheck–ElementtoRelay(Turn the ignition switch to OFF. Disc
onnect harness
from element terminal. Check for corrosion. Trace wiring harness from element
to IAH relay. Ensure the
correct relay terminal is being tested.)
Element terminal 1 to relay
output terminal 1
<5Ω If > 5 Ω, check for a corroded terminal or an open circuit.
Element terminal 2 to relay
output terminal 2
<5Ω If > 5 Ω, check for a corroded terminal or an open circuit.
Voltage Check at Relays – Battery Feed Wires (Starter)
Relay 1: Battery feed terminal
to gnd
B+
If < B+, check for dead battery, open in IAH harness, or
open in truck battery harness.
Relay 2: Battery feed terminal
to gnd
B+
If < B+, check for dead battery, open in IAH harness, or
open in truck battery harness.
Voltage Check at Relays – Output (Output State Test) (Turn the ignit ion switch to ON. Run G lowplug /
Inlet Air Heater Output State Test. For help, see “Inlet Air Heater Output State Test” in Section 3 (page 68).)
Relay 1: Relay output post to
gnd
B+
If < B+, check for dead battery, open IAH harnes
s, open
in truck battery harness, faulty IAH relay, E
CM for IAH
programming, or open relay control circuit
from ECM.
Relay 2: Relay output post to
gnd
B+
If < B+, check for dead battery, open IAH harness, open
in truck battery harness, faulty IAH relay, ECM for IAH
programming, or open relay control circuit from ECM.
Actuator Control Voltage Check at Relay Connection (Disconnect control wiring from relay. Turn the
ignition switch ON. Run the Glow Plug / Air Heater O utput State Test. For help, see “Inlet Air Heater Output
StateTest”inSection3(page68).)
Element 1: A to gnd B+
If < B+, do Actuator Control Voltag
e Check at ECM (page
449).
Element 1: A to B B+
If < B+, do Harness Resistance Check – Relay to 12-pin
Connector. (page 450).
Element 2: A to gnd B+
If < B+, do Actuator Control Voltage Check at ECM (page
449).
Element 2: A to B B+
If < B+, d o Harness Resis
tance Check – Relay to 12-pin
Connector. (page 450).
NOTE: If both relays are < B+, check wiring back to the ECM and 12-pin connector. Verify ECM programming.
The Glowplug / IAH parameter should be option 2 (IAH).
Actuator Control Voltage Check at ECM (Connect breakout box [X1 only] to ECM. Turn the ignition switch
to on. Run the Glow Plug / Inlet Air Heater Output State Test. For help, see “Inlet Air Heater Output State
Test” in Section 3 (page 68).)
Output Stat e Test
High
X1–17 to gnd B+
If < B+, and ECM is programmed correctly, replace the
ECM.
Output Stat e Test Low
X1–17 to gnd 0 V
If > 0.25 V, and
ECM is programmed correctly, replace the
ECM.
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.
To Next Page
Loading...
Need help?
General