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7 ELECTRONIC CONTROL SYSTEMS DIAGNOSTICS
EFP Circuit Operation
Figure 438 EFP circuit diagram
The EFP sensor is supplied with a 5 V reference
voltage at Pin 2 from ECM Pin X1–14. The EFP
sensor is grounded at Pin 1 from ECM Pin X1–6. The
EFP sensor returns a variable voltage signal from Pin
3 to ECM Pin X2–16.
Fault Detection / Management
The ECM will ignore the EFP signal when the signal
is detected to be out of range or an incorrect value is
read.
EFP Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the
flashes from the amber and red ENGINE lamp.
DTC 136
EFP signal out-of-range low
•
DTC 136 is set by ECM when the EFP signal is
less than 0.039 V for more than 0.35 second.
•
DTC 136 can be set due to an open or short to
ground on the signal circuit, a failed EFP sensor
or an open V
circuit or V
REF
•
When DTC 136 is active the amber ENGINE lamp
is not illuminated.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
short to ground.
REF
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
DTC 137
EFP signal out-of-range high
•
DTC 137 is set by the ECM when the EFP signal
is greater than 4.9 V for more than 0.35 second.
•
DTC 137 can be set due to a signal circuit short
to V
or B+ or a failed EFP sensor.
REF
When DTC 137 is active the amber ENGINE lamp
•
is not illuminated.
DTC 371
EFP is above normal operating range
•
DTC 371 is set by ECM when measured fuel
pressure is greater than expected pressure by
100 kPa (15 psi) for more than 60 seconds.
•
DTC 371 can be set due to debris in fuel regulator
valve, failed fuel regulator valve, open signal
ground, V
shorted to a voltage source greater
REF
than 5.5 V, bias high circuit, or failed EFP sensor.
•
When DTC 371 is active the amber FUEL FILTER
lamp will not illuminate
407
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