TROUBLE CODE DIAGNOSTICS - 7.4L MPI
SERVICE MANUAL NUMBER 23
Code 33 (2 of 3): Manifold Absolute Pressure (MAP) Sensor Circuit (Non-Scan)
High Signal Voltage
TEST DESCRIPTION:
STEP 2. This step will determine if there is an adequate vacuum supply to the MAP sen-
sor. If the vacuum gauge reading is erratic, refer to the “Rough or Unstable Idle” symp-
tom.
STEP 3. This step simulates a DTC 34. If the ECM recognizes the low signal voltage
and sets a DTC 34, the ECM and wiring are OK.
STEP 4. This step checks to see if CKT 814 is open.
STEP 5. Low manifold vacuum may result from a restriction in the MAP sensor hose or
from vacuum leaks in the engine induction system.
STEP
ACTION
VALUE
YES
NO
PROCEED TO
Go to
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
OBD
System
Check
1
2
–
Step 2
1. Ignition “OFF.”
2.
Disconnect vacuum at MAP sensor and
install a vacuum gauge.
3.
Start engine and increase RPM to 1000 in
neutral.
4.
The vacuum reading should be steady.
14
Hg (45.5 Step 3
kPa)
In.
Is the vacuum reading steady and above
the specified value?
Step 5
1.
“Normal Mode.”
Marine Diagnostic Code Tool switched to the
3
2.
3.
4.
Marine Diagnostic Code Tool indicates a
stored trouble code.
Ignition “OFF”.
Disconnect MAP sensor harness connector.
Start engine and idle for 2 minutes or until
5.
Ignition “ON,” engine “OFF”.
6.
“Service Mode” and note trouble code.
Switch Marine Diagnostic Code Tool to the
Is trouble code 34 present?
–
Step 6
Step 4
1.
nected.
MAP sensor harness connector discon-
4
2.
Ignition “ON” engine “OFF.”
3.
(CKT 814) to harness terminal “C” (CKT
416E).
Connect DVOM from harness terminal “A”
Is voltage reading above the specified val-
ue?
4
Volts
Step 7
Step 8
Page 5G-20
90-861326--1 MARCH 1999
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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