SERVICE MANUAL NUMBER 23
TROUBLE 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)
–
Step 3
Step 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)
–
Step 4
Step 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 position sensor signal)
–
Step 7
Step 10
(throttle osition sensor signal).
Is test light on?
–
Ste 7
Ste 10
5
Connect DVOM between harness terminal “C”
and engine ground (–)
–
Step 8
Step 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
–
Step 14
Step 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 position sensor signal)
–
Step 11
Step 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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