372 7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
ECL Pin-Point Diagnostics
Figure 420 ECL system circuit diagram
The ECL circuit may require the use of vehicle
circuit diagrams. See truck Chassis Electrical Circuit
Diagram Manual for circuit numbers, connector and
fuse locations.
Coolant Level Sensor Connector (Disconnect sensor from harness and turn the ignition switch to ON.
Test with coolant level full.) Note: After removing connector, inspect for damaged pins, corrosion, or loose
pins. Repair as required.
Test Point
Spec Comment
Atognd 5V±0.5V
If voltage < 5 V, check for open signal circuit or failed ECM.
Btognd 0V
If voltage > 0 V, check for signal circuit shorted to another circuit
Sensor Resistance Checks (Disconnect sensor connector and measure across sensor)
AtoB
>1kΩ If < 1 kΩ, check for low coolant, failed sensor, or shorted sensor harness.
Harness Resistance Checks (Turn the ignition switch to OFF. Connect breakout box to chassis harness
only. Disconnect sensor.)
Btognd
<5Ω If > 5 Ω, check for open ground wire
X3-4 to A
<5Ω If > 5 Ω, check for open signal wire (breakout box connected)
Operational Voltage Checks for ECL (Check with breakout box connected and sensor connected. Turn
theignitionswitchtoON.)
X3-4 to X3-7 5 V
Voltage > 4.3 V with tank full. Voltage < 3.4 V with tank empty (use
breakout box)
ECL Diagnostic Trouble Codes
DTC 236 = Signal voltage between 3.4 V and 4.3 V more than 2.0 seconds.
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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