Mercury MerCruiser MCM 454 Mag MPI Service Manual page 755

TROUBLE CODE DIAGNOSTICS - 7.4L MPI
Code 21 (1 of 2): Throttle Position (TP) Sensor Circuit (Non-Scan) Signal
Voltage High
STEP
1
2
3
4
5
6
7
Index
Page 5G-10
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ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Marine Diagnostic Code Tool switched to the
normal or "OFF" Mode.
2. Ignition "OFF."
3. Disconnect throttle position sensor harness
connector.
4. Start engine and idle for 2 minutes or until
Marine Diagnostic Code Tool indicates a
stored trouble code.
5. Ignition "ON", engine "OFF."
6. Switch Marine Diagnostic Code Tool to "Ser-
vice Mode" and note the trouble code.
Is the trouble code 22 present?
1. TP sensor harness connector disconnected.
2. Ignition "ON," engine "OFF."
3. Connect DVOM from harness terminal "B"
(CKT 813) to harness terminal "A" (CKT 416). (CKT 813) to harness terminal A (CKT 416).
Is voltage reading above specified value?
Locate and repair intermittent faulty connec-
tions. If OK, replace faulty TP sensor. Is action
complete?
Locate and repair open in CKT 813. If a prob-
lem is found, repair as necessary. Was a prob-
lem found?
Locate and repair short to voltage in CKT 417.
If a problem is found, repair as necessary. Was
a problem found?
Repair faulty ECM connect ion or replace faulty
ECM. Is action complete?
SERVICE MANUAL NUMBER 23
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
– Step 4 Step 3
4 Volts Step 6 Step 5
–
– Step 7
Verify
Repair Re air
– Step 7
–
90-861326--1 MARCH 1999
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