Isuzu engine C22NE / 22LE / 20LE. Manual — part 86
DRIVEABILITY AND EMISSIONS 6E1-173
0.5
YEL/
GRN
0.5
GRN
0.5
RED
0.5
RED
0.5
GRN
0.5
RED
Manifold
Absolute
Pressure
(MAP)
Sensor
F10
B2
0.5
GRN
B7
A3
5 Volt
Reference
Signal
MAP Sensor
Input
Sensor
Ground
0.75
L
B8
0.75
G
B1
A B
C
Intake
Air Temperature
Sensor
Throttle Position
Sensor
Engine
Control
Module
(ECM)
HI
OUT
LO
0.5
G
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 33)
MANIFOLD ABSOLUTE PRESSURE (MAP) TOO HIGH
Circuit Description
The manifold absolute pressure (MAP) sensor
responds to changes in intake manifold pressure. The
MAP sensor signal voltage to the engine control
module (ECM) varies from below 2 volts at idle (low
manifold pressure) to above 4 volts with the ignition
ON, engine not running or at wide-open throttle (high
manifold pressure).
A "speed density" method of determining engine load
is used. This is calculated using inputs from the MAP
sensor, the CKP Sensor, and the Intake Air
Temperature (IAT) sensor. The MAP sensor is the
main sensor used in this calculation, and measuring
engine load is its main function. The ECM monitors
the MAP signals for voltages outside the normal range
of the MAP sensor. This code defects a short to MAP
signal voltage in the MAP sensor circuit. Diagnostic
Trouble Code 33 will be set.
Conditions for Setting the DTC
• No TP sensor Diagnostic Trouble Codes 21 or 22
present.
• Engine is running.
• Not in power enrich mode.
• Throttle Position Sensor value is less than 1%.
• Altitude Compensated Manifold Absolute Pressure
is greater than 95kpa.
Action Taken When the DTC Sets
• The ECM will illuminate the malfunction indicator
lamp (MIL).
Conditions for Clearing the MIL/DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
6E1-174 DRIVEABILITY AND EMISSIONS
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, shorts to Ground, shorts to Battery
positive, and Open circuits. If the harness appears
to be OK, observe the MAP display on the Scan
Tool while moving connectors and wiring harnesses
related to the sensor. A change in the display will
indicate the location of the fault.
DTC (Flash DTC = 33)
Manifold Absolute Pressure (MAP) Too High
Step
Action
Value(s)
Yes
No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
-
Go to Step 2
Go to OBD
System
Check
2
1. If the engine idle is rough, unstable or incorrect, repair
the idle problem before using this chart.
Refer to Symptoms section.
2. With the engine idling, note the MAP value on the Scan
Tool.
Is the MAP reading above the specified value?
About 4V
90 kPa
Go to Step 4
Go to Step 3
3
1. Ignition ON engine OFF.
2. Using the Scan Tool, monitor info for Diagnostic
Trouble Code 33.
Does the Scan Tool indicate Diagnostic Trouble Code 33
failed?
-
Go to Step 4
Refer to
Diagnostic
Aids
4
1. Ignition OFF.
2. Disconnect the MAP sensor electrical connector.
3. Ignition ON.
4. Observe the MAP value displayed on the Scan Tool.
Is the MAP value near the specified value?
0V
10.3 Kpa
Go to Step 5
Go to Step 6
5
Check the MAP sensor signal circuit, between the MAP
sensor and the Engine control Module (ECM), for a short
to voltage.
Was the problem found?
-
Verify Repair
Go to Step 12
6
Check the MAP sensor signal circuit, between the MAP
sensor and the ECM for the following conditions:
• A short to ground
• An open circuit
Was the problem found?
-
Verify repair
Go to Step 7
7
Check the 5 volt signal circuit, between the MAP sensor
and the ECM for the following conditions:
• A short to ground
• An open circuit
• A short to voltage
Was the problem found?
-
Verify Repair
Go to Step 8
DRIVEABILITY AND EMISSIONS 6E1-175
DTC (Flash DTC = 33)
Manifold Absolute Pressure (MAP) Too High (Cont'd)
Step
Action
Value(s)
Yes
No
8
1. Ignition OFF.
2. Place a fused jumper between the MAP sensor circuit
and the 5 volt signal circuit, both at the wiring harness'
MAP sensor connector.
3. Ignition ON, Engine OFF.
4. Observe the MAP value displayed on the Scan Tool.
Does the Scan Tool read the following value?
5 Volts
104 kPa
Go to Step 9
Go to Step 12
9
Check the MAP sensor ground circuit, between the MAP
sensor and the ECM, for the following conditions:
• A short to ground
• An open circuit
• A short to voltagen
Was the problem found?
-
Verify Repair
Go to Step 10
10
1. Ignition OFF.
2. Place a Digital Multimeter (DVM), set to measure
voltage between the ground circuit and the 5 volt signal
circuit, both at the wiring harness' MAP sensor
connector.
3. Ignition ON, Engine OFF.
Does the DVM read the following value?
5 Volts
Go to Step 11
Go to Step 12
11
Replace the MAP Sensor.
Verify Repair.
-
-
-
12
Replace the EPROM or ECM.
Verify Repair.
Note) Refer to 6E1-243.
-
-
-
6E1-176 DRIVEABILITY AND EMISSIONS
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