Mercury MerCruiser MCM 454 Mag MPI Service Manual page 710

SERVICE MANUAL NUMBER 23
Code 33 (3 of 3): Manifold Absolute Pressure (MAP) Sensor Circuit (Non-Scan)
Index
90-861326--1 MARCH 1999
Downloaded from https://needmanual.com/
STEP
Is voltage reading over 4 volts?
5 1. Ignition OFF.
2. Connect a test light to battery positive
(B+).
3. Touch test light to harness terminal "B"
(MAP sensor signal).
Is test light on?
6 1. Disconnect ECM.
2. Touch test light connected to battery pos-
itive (B+) to harness terminal "B." (See Note)
Connect DVOM from MAP sensor harness ter-
minal "C" to a good ground on engine. minal C to a good ground on engine.
7 7
Is voltage reading over 4 volts?
Connect DVOM between harness terminal "B"
8
and engine ground (–).
Is voltage reading over 4 volts?
9 MAP sensor faulty.
10 CKT 432 shorted to voltage.
11 CKT 432 shorted shorted to ground.
12 Faulty ECM.
Faulty connection at ECM, CKT 416 open,
13
shorted to ground, or faulty ECM.
Faulty connection at ECM, CKT 814 open or
14
faulty ECM.
Open CKT 432, faulty connection at ECM or
15
faulty ECM.
16 Repair low or unsteady vacuum problem.
TROUBLE CODE DIAGNOSTICS - 454/502 MAG MPI & 8.2L MPI
ACTION VALUE YES NO
PROCEED TO
– Step 5 Step 8
– Step 6 Step 9
– Step 11 Step12
– – Ste 14 Step 14 Ste 13 Step 13
– Step 10 Step 15
– –
– –
– –
– –
– –
– –
– –
– –
Page 5F-13
–
–
–
–
–
–
–
–