Mercury MerCruiser MCM 454 Mag MPI Service Manual page 721

TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
Code 21 (2 of 3): Throttle Position (TP) Sensor Circuit (Scan)
TEST DESCRIPTION:
Number(s) below refer to step number(s) on the diagnostic table.
Step 2: With throttle closed the TP sensor should read between .3 and .8 volt. If it does not,
check throttle cable adjustment or for bent linkage.
Step 4: With the TP sensor disconnected, the TP voltage should go low if the ECM and wir-
ing are OK.
Step 7: Probing CKT 813 with a DVOM to CKT 416 checks the sensor ground. A faulty sen-
sor ground will cause a Code 21.
STEP
1
2
3
4
4
5 5
6
Index
Page 5F-24
Downloaded from https://needmanual.com/
ACTION
Was the "On-Board Diagnostic" (OBD) System
Check Performed?
1. Throttle closed.
2. Ignition ON.
Does scan tool indicate throttle position
sensor voltage greater than 4 volts?
Does scan tool indicate throttle position
sensor voltage less than .36 volts?
Code 21 is intermittent, refer to "Diagnostic
Aids" on facing page.
1. Ignition OFF.
2. Disconnect throttle position sensor electrical
connector. Jumper throttle position sensor har-
ness terminals "A" and "C" together.
3. Ignition ON.
4. Scan tool should indicate throttle position
sensor voltage greater than 4 volts.
Does it?
1. Ignition OFF.
2. Disconnect throttle position sensor connec- 2 Disconnect throttle position sensor connec
tor.
3. Ignition ON.
Does scan tool indicate voltage over 4 Does scan tool indicate voltage over 4
volts?
1. Ignition OFF. g
2. Connect DVOM between throttle osition 2 Connect DVOM between throttle position
sensor harness terminal "A" and ground.
3. Ignition ON. 3 Ignition ON
Is voltage over 4 volts?
SERVICE MANUAL NUMBER 23
VALUE YES NO
PROCEED TO
Go to
OBD
– Step 2
System
Check
Step 5 Step 3
Step 4 Step 3
– –
– Step 11 Step 6
– Step 8 Step 7
– Step 9 Step 10
90-861326--1 MARCH 1999
–