SERVICE MANUAL NUMBER 23
TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 22 (3 of 3): Throttle Position (TP) Sensor Circuit (Scan) Low Signal
Voltage
STEP
ACTION
VALUE
YES
NO
PROCEED TO
Locate and repair open or short to ground in
CKT 416. Also check CKT 416E to the MAP
sensor for a short to ground. If a problem is
found, repair as necessary. Was a problem
found?
6
7
–
–
Step 9
Verify
Repair
Locate and repair open or short to ground in
CKT 417. If a problem is found, repair as nec-
essary. Was a problem found?
Step 9
8
9
Replace faulty TP sensor. Is action complete?
–
–
–
–
Repair faulty ECM connections or replace
faulty ECM. Is action complete?
Code 23 (1 of 3): Intake Air Temperature (IAT) Sensor Circuit (Scan) - Low
Temperature Indicated
a
c
B
A
d
b
a - Intake Air Temperature Sensor
b - To TP Sensor
c - IAT Sensor Signal
d - Sensor Ground
CIRCUIT DESCRIPTION:
The Intake Air Temperature (IAT) Sensor uses a thermistor to control the signal voltage to
the ECM. The ECM applies a voltage on CKT 472 to the sensor. When the intake air is cold,
the sensor (thermistor) resistance is high, therefore, the ECM will see high signal voltage.
As the intake air warms, the sensor resistance becomes less, and the voltage drops. At nor-
mal engine operating temperature, 160-180°F (71-82°C), the voltage will measure about
1.5
to 2.0 volts.
90-861326--1
MARCH 1999
Page 5G-47
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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