Isuzu engine C22NE / 22LE / 20LE. Service manual — part 87
DRIVEABILITY AND EMISSIONS 6E1-177
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 = 34)
MANIFOLD ABSOLUTE PRESSURE (MAP) TOO LOW
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
(10-104 kpa) of the MAP sensor. If the ECM detects a
MAP signal voltage that is excessively low, Diagnostic
Trouble Code 34 will be set.
Conditions for Setting the DTC
• Manifold Absolute Pressure is less than 14 kpa and
one of following condition is met the DTC will set.
Condition A:
• Malfunction 21 not present and rpm is less than
1050.
Or,
Condition B:
• Malfunction 21 not present and rpm is greater
than 1050 and TP opening is greater than
18.75% and ignition ON.
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 -
6E1-178 DRIVEABILITY AND EMISSIONS
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.
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.
• A faulty 5 volt reference circuit could also set a TP
Sensor Diagnostic Trouble Code because the two
sensors share the same 5 volt reference pin at the
ECM.
DTC (Flash DTC = 34)
Manifold Absolute Pressure (MAP) Too Low
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. Ignition ON engine OFF.
2. With the throttle closed, observe the MAP value
displayed on the Scan Tool.
Is the MAP value near the specified value?
0V
10.3 kPa
at sea level
Go to Step 4
Go to Step 3
3
1. Ignition ON, engine OFF.
2. Using a Scan Tool, monitor info for Diagnostic Trouble
Code 34.
Does the Scan Tool indicate Diagnostic Trouble Code 34
failed?
-
Go to Step 4
Refer to
Diagnostic
Aids
4
1. Ignition OFF.
2. Disconnect the MAP sensor electrical connector.
3. Jumper the 5 volt reference circuit and the MAP signal
together at the MAP sensor harness connector.
4. Ignition ON.
5. Observe the MAP value displayed on the Scan Tool.
Is the MAP value near the specified value?
5V
104 kPa
Go to Step 10
Go to Step 5
5
1. Disconnect the jumper.
2. Connect a test light between B+ and the MAP sensor
signal circuit at the MAP sensor harness connector.
3. Observe the MAP value displayed on the Scan Tool.
Is the MAP value near the specified value?
5V
104 kPa
Go to Step 6
Go to Step 8
DRIVEABILITY AND EMISSIONS 6E1-179
DTC (Flash DTC = 34)
Manifold Absolute Pressure (MAP) Too Low (Cont'd)
Step
Action
Value(s)
Yes
No
6
1. Ignition OFF.
2. Disconnect the ECM and check the 5 volt reference
circuit for an open or short to ground.
3. If the 5 volt reference circuit is open or shorted to
ground, repair it as necessary.
Was the 5 volt reference circuit open or shorted to
ground?
-
Verify repair
Go to Step 7
7
Check the 5 volt reference circuit for a poor connection at
the ECM and replace the terminal if necessary.
Did the terminal require replacement?
-
Verify repair
Go to Step 11
8
1. Ignition OFF.
2. Disconnect the ECM, and check the MAP signal circuit
for an open,short to ground, or short to the sensor
ground circuit.
3. If the MAP sensor signal circuit is open or shorted to
ground, repair it as necessary.
Was the MAP signal circuit open or shorted to ground?
-
Verify repair
Go to Step 9
9
Check the MAP sensor signal circuit for a poor connection
at the ECM and the MAP sensor; replace the terminal if
necessary.
Did the terminal require replacement?
-
Verify repair
Go to Step 11
10
Replace the MAP sensor.
Is the action complete?
-
Verify repair
-
11
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
Is the action complete?
-
Verify repair
-
6E1-180 DRIVEABILITY AND EMISSIONS
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст