PleasureCraft Engine Group 5.0L, Diagnostic Manual, Page: 236 / 337

5 - 94 Diagnosis 5.0/5.7/6.0/8.1L
MEFI 4 - PCM
DTC 33 - Manifold Absolute Pressure (MAP) Sensor Circuit - Signal Voltage High
(Scan Diagnostics)
•
If the idle is rough or unstable, refer to Symptoms for
items which may cause an unstable idle.
•
With the ignition “ON,” engine “OFF,” the manifold
pressure is equal to atmospheric pressure and the
signal voltage will be high. This information is used by
the ECM as an indication of altitude and is referred to
as BARO. Comparison of this BARO reading, with a
known good MAP sensor, is a good way to check the
accuracy of a “suspect” sensor. Reading should be the
same, plus or minus 0.4 volt.
•
If DTC 14 is also set, check for open in ground CKT
814.
•
If a MAP sensor circuit failure is present, the TP sensor
default value will be used along with the MAP sensor
default value.
After repairs, clear DTC’s following “Clear DTC’s Procedure.”
Failure to do so may result in DTC’s not properly being
cleared.
Test Description
2. This step will determine if there is an adequate vacuum
supply to the MAP sensor. If the vacuum gauge
reading is erratic, refer to the “Rough or Unstable Idle”
symptom.
4. 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.
5. This step checks for an open in ground CKT 814.
Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to
changes in manifold pressure (vacuum). The ECM receives
this information as a signal voltage that will vary from about
1.0-1.5 volts at idle to about 4.0-4.5 volts at Wide Open
Throttle (WOT).
If the MAP sensor fails, the ECM will substitute a default
MAP value that will vary with RPM.
The MAP sensor voltage of 5 volts is delivered to the MAP
sensor through CKT 416E. CKT 814 is the ground circuit
for the MAP sensor. The MAP signal CKT 432 will send
a voltage signal back to the ECM according to what the
manifold pressure is.
Diagnostic Aids
Check for the following conditions:
•
Poor connection at ECM. Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals and
poor terminal to wire connection.
•
Damaged harness. Inspect the wiring harness for
damage. If the harness appears to be OK, observe
the MAP sensor display on the scan tool while moving
connectors and wiring harnesses related to the MAP
sensor. A change in the MAP sensor display will indicate
the location of the fault.
8
2 J2
3
GRY 416E
LT GRN 432
BLK 814
BLK 814
B A
C
Manifold
Absolute
Pressure
(MAP)
Sensor
(6.0/8.1L)
Engine
Control
Module
(ECM)
Map
Sensor
Signal
Sensor
Ground
Engine
Control
Module
(ECM)
S125
S123
J2
M4055a
2-12-04
GRY 416
5 Volt
Reference
From ECT
Sensor
From TP
Sensor
To TP
Sensor
8
21
2 J2
3
GRY 416E
LT GRN 432
BLK 814
BLK 814
BLK 814
4
1
3
Manifold
Absolute
Pressure
(MAP)/Intake
Air Temperature
(IAT) Sensor
(5.0/5.7L)
Engine
Control
Module
(ECM)
Map
Sensor
Signal
Sensor
Ground
Engine
Control
Module
(ECM)
2
S125
S123
PPL 472
J2
M4055
9-18-02
GRY 416
5 Volt
Reference IAT Sensor
Signal
From ECT
Sensor
From TP
Sensor
To TP
Sensor