Code 33: Manifold Absolute Pressure (MAP) Sensor Circuit (Non-Scan)
(1 Of 2)
814
BLK
MAP AND
ECT
ECT SENSOR
GROUND
CIRCUIT DESCRIPTION:
DIAGNOSTIC AIDS:
The Manifold Absolute Pressure (MAP) sensor re-
sponds to changes in manifold pressure (vacuum).
The ECM receives this information as a signal volt-
age that will vary from about 1-1.5 volts at closed
throttle idle, to 4-4.8 volts at Wide Open Throttle
(W.O.T.) (low vacuum).
An intermittent problem may be caused by a poor or
corroded connection, rubbed through wire connec-
tion, a wire that is broken inside the insulation, or a
corroded wire.
Any circuitry that is suspected as causing the inter-
mittent complaint should be thoroughly checked for
backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, poor
terminal-to-wiring connections, corroded terminals
and/or wiring, or physical damage to the wiring har-
ness. After repairs, clear codes following “Clearing
Codes” in “ECM Self-Diagnostics.” Failure to do so
may result in codes not properly being cleared. If
Code 14 is also set, check for open ground CKT 814.
MAP SENSOR
IftheMAPsensorfails,theECMwillsubstituteafixed
MAP value and use the engine RPM to control fuel
delivery.
TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the
diagnostic chart.
1.
This step will determine if there is an adequate
vacuum supply to the MAP sensor. If the gauge
reading is erratic, refer to “Stalling, Rough, Un-
stable or Incorrect Idle” in “Troubleshooting.”
ALTITUDE
VOLTAGE
RANGE
Feet
Meters
Below 1,000
1,000-2,000
2,000-3,000
3,000-4,000
4,000-5,000
5,000-6,000
6,000-7,000
7,000-8,000
8,000-9,000
9,000-10,000
Below 305
305-610
3.8-5.5 V
3.6-5.3 V
3.5-5.1 V
3.3-5.0 V
3.2-4.8 V
3.0-4.6 V
2.9-4.5 V
2.8-4.3 V
2.6-4.2 V
2.5-4.0 V
2.
3.
4.
5.
6.
Low manifold vacuum may result from vacuum
leaks in the engine induction system.
610-914
This step checks for a voltage from terminal “C”
914-1219
1219-1524
1524-1829
1829-2133
2133-2438
2438-2743
2743-3048
(5
volt reference) to terminal “A” (sensor ground).
This step will identify if the problem is in the sup-
ply 5 V reference or ground circuit.
This step determines if the MAP signal circuit to
the ECM is open.
This step completes the test for the ECM and wir-
ing. If the test light is not ON, the MAP sensor has
an internal problem. To confirm an internal MAP
sensor problem, use the MAP output voltage
check chart.
LOW ALTITUDE = HIGH PRESSURE = HIGH VOLTAGE
Index
5C-92 - ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY)
90-823224--2 796
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1993, 1994, 1995, 1996, 1997 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
(4 votes, average: 4.5 out of 5)
Marine readers have rated 1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 4.5 out of 5.0 based on 4 product reviews. Hugely helpful service manual! Perfect. Thank you!
Manuals are all Important for Technician
This book is invaluable if you do your own repairs. Great book.
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