Mercury MerCruiser MIE 7.4L MPI - Page 705

SERVICE MANUAL NUMBER 23TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
Page 5F-8 90-861326--1 MARCH 1999
Code 21 (2 of 2): Throttle Position (TP) Sensor Circuit (Non-Scan)
STEP ACTION VALUE YES NO
PROCEED TO
1
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
– Step 2
Go to
OBD
System
Check
2 1. Ignition OFF.
2. Disconnect throttle position sensor har-
ness connector.
3. Ignition ON.
4. Connect DVOM from harness terminal
“A” (5 volt reference to harness terminal “B”
(d)
–
Ste
p
3
Ste
p
6
(sensor ground).
Is voltage reading over 4 volts?
–
Ste
3
Ste
6
3
Connect DVOM from harness terminal “A”
(CKT 416) to harness terminal “C” (throttle
i i i l CKT 417)
–
Ste
p
4
Ste
p
5
3
position sensor signal, CKT 417).
Is voltage reading over 4 volts?
–
Ste
4
Ste
5
4 1. Ignition OFF.
2. Connect a test light to battery positive
(B+).
3. Touch test light to harness terminal “C”
(throttle
p
osition sensor signal)
–
Ste
p
7
Ste
p
10
(throttle
osition
sensor
signal)
.
Is test light on?
–
Ste
7
Ste
10
5
Connect DVOM between harness terminal “C”
and engine ground (
–
)
–
Ste
p
8
Ste
p
9
5
and
engine
ground
(–)
.
Is voltage over 4 volts?
–
Ste
8
Ste
9
6
Connect DVOM from throttle position sensor
harness terminal “A” to a good ground on
i
–
Ste
p
14
Ste
p
13
6
engine.
Is voltage over 4 volts?
–
Ste
14
Ste
13
7 1. Disconnect ECM.
2. Touch test light to harness terminal “C”
(throttle
p
osition sensor signal)
–
Ste
p
11
Ste
p
12
(throttle
osition
sensor
signal)
.
Is test light on?
–
Ste
11
Ste
12
8 Check for CKT 417 shorted to voltage. – – –
9
Open or CKT 417, faulty connection at ECM or
faulty ECM.
– – –
10 Throttle position sensor faulty. – – –
11 Check for CKT 417 shorted to ground. – – –
12 Faulty ECM. – – –
13
Faulty connection at ECM, CKT 416, shorted
to ground or faulty ECM.
– – –
14
Faulty connection at ECM, CKT 813 open or
faulty ECM.
– – –
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