7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS 401
Output State Test - Voltage Checks at Fan Relay (Check with relay breakout harness
connected with
relay. Turn the ignition switch to ON. Run the Output State Tests. For help, see “
Diagnostic Software
Operation” in Section 3 (page 68) for procedure to run the Low and High O utput Stat
eTests.)
Test State/Po in t Spec Comment
Output State Test - Low
30 to gnd B+ ± 0.5 V
If < B+, do Harness Resistance Checks.
86 to gnd B+ ± 0.5 V
If < B+, do Harness Resistance Checks.
85 to gnd 0 V to 0.25 V
If > 0.25 V, check for open circuit, short to volt age
source, ECM programming, or failed ECM. Do Harness
Resistance Checks.
87 to gnd B+ ± 0.5 V
If < B+, and previous checks (30, 86, 85 to gnd) are
within specification, replace relay.
87A to gnd 0 V to 0.25 V
If > 0.25 V, and previous checks (30, 86, 85 to gnd)
arewithinspecification, but 87 to gnd is not within
specification, replace relay.
Output State Test - High
30 to gnd B+ ± 0.5 V
If < B+, do Harness Resistance Checks.
86 to gnd B+ ± 0.5 V
If > B+, do Harness Resistance Checks.
85 to gnd B+ ± 0.5 V
If < B+, check for open circuit, ECM programming, or
failed ECM. Do Harness Resistance Chec ks.
87 to gnd B+ ± 0.5 V
If > 0.25 V, and previous checks (30
, 86, 85 to gnd) are
within specification, replace re
lay.
87A to gnd B+ ± 0.5 V
If < B+, and p revious checks (30, 86, 85 to gnd)
arewithinspecification, but 87 to gnd is not within
specification, replace relay.
Output State Test - Voltage Checks at ECM (Disconnect X3 and X4 from ECM. Connect breakout box
X3 and X4 to ECM and wiring harness. Disconnect relay. Turn the ignition switch to ON. Run the Output
State Tests. For help, see “Diagnostic Software Operation” in Section 3 (page 68) for procedure to run
the Low and High Output Sta te Tests.)
Output State Test - Low
X3–3 to X4–14 B+ ± 0.5 V
If < B+, verify that ECM is programmed correctly. If
ECM is programmed correctly, replace ECM.
Output State Test - High
X3–3 to X4–14 0 V to 0.25 V
If > 0.25 V, verify t
hat ECM is programmed correctly.
If ECM is prog r amm
ed correctly, replace 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.