Isuzu engine C22NE / 22LE / 20LE. Service manual — part 100
DRIVEABILITY AND EMISSIONS 6E1-229
0.5
R
0.5
B/R
0.5
G
Engine
Control
Module
(ECM)
Crank
Angle
Sensor
F1
E5
B5
Tacho
Meter
Meter
Fuse
15A
2
1
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 91)
TACHO OUT LOW ERROR
Circuit Description
Based on the information from the Crank Position
Sensor (CKP), X58 reference signal is generated at
each rotation of the crankshaft.
Engine Control Module (ECM) converts X58 reference
signal into rectangle wave and delivers it as output
signal to drive the pulse motor of the crankshaft.
When the wave length of the output signal is long, the
tacho meter indicates the engine speed is low, and
vise versa.
This malfunction detects a low impedance short to
ground or open contact on the Tacho output, the
Diagnostic Trouble Code 91 will be set.
Conditions for Setting the DTC
• Driver feedback information shows a low state at its
operation even when commanded low.
Action Taken When the DTC Sets
• The ECM will turn ON the Malfunction Indicator
Lamp
Conditions for Clearing the 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.
Diagnostic Aids
• Poor connections or a damaged harness - Inspect
the harness connections for: backed out terminals,
imprope, mating or damaged terminals. Also check
for open circuit, short to ground, and short to
voltage.
6E1-230 DRIVEABILITY AND EMISSIONS
• This malfunction detects a low impedance short to
ground or open contact on the ECM out put circuit.
DTC (Flash DTC = 91)
Tacho Out Low Error
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 OFF.
2. Check for a faulty connection or damaged terminals at
the ECM connector.
Was a problem found?
-
Verify repair
Go to Step 3
3
Check for a faulty connection or damaged terminals at the
ECM connector.
Was a problem found?
-
Verify repair
Go to Step 4
4
1. Check for an open or short to ground in the circuit
between the meter cluster connector and the ECM
connector.
If a problem is found, repair as necessary.
-
Verify repair
Go to Step 5
5
1. Check for an open circuit between the meter cluster
connector and the ground.
If a problem is found, repair as necessary.
-
Verify repair
Go to Step 6
6
1. Check for an open circuit between the meter cluster
and battery feed.
If a problem is found, repair as necessary.
-
Verify repair
Go to Step 7
7
1. Disconnect the meter cluster Panel.
2. Check the tacho meter circuit for an open.
Was a problem found?
-
Go to Step 5
Go to Step 9
8
1. Disconnect the ECM and CKP sensor.
2. Check for an open in the 58X reference circuit between
the connector and the ECM harness connector.
3. If a problem is found, repair as necessary.
Was a problem found?
-
Verify repair
Go to Step 9
9
1. Reconnect the ECM and CKP sensor.
2. Connect a Digital Voltmeter (DVM) to measure voltage
on the 58X reference circuit at the ECM connector.
3. Observe the voltage while cranking the engine.
Is the voltage near the specified value?
2.5V
Go to Step 12
Go to Step 10
10
Check the connections at the CKP sensor and replace the
terminals if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 11
11
Replace the CKP sensor.
Is the action complete?
-
Verify repair
-
12
Check connections at the ECM and replace the terminals
if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 13
13
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
DRIVEABILITY AND EMISSIONS 6E1-231
0.5
R
0.5
B/R
0.5
G
Engine
Control
Module
(ECM)
Crank
Angle
Sensor
F1
E5
B5
Tacho
Meter
Meter
Fuse
15A
2
1
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC =92)
TACHO OUT HIGH ERROR
Circuit Description
Based on the information from the Crank Position
Sensor (CKP), X58 reference signal is generated at
each rotation of the crankshaft.
Engine Control Module (ECM) converts X58 reference
signal into rectangler wave and delivers it as output
signal to drive the pulse motor of the crankshaft.
When the wave length of the output signal is long, the
tacho meter indicates the engine speed is low, and
vise versa.
This malfunction detects a low impedance short to
battery or on the Tacho output, then Diagnostic
Trouble Code 92 will be set.
Conditions for Setting the DTC
• Driver feedback information shows a low state at its
operation even when commanded low.
Action Taken When the DTC Sets
• The ECM will turn ON the Malfunction Indicator
Lamp
Conditions for Clearing the 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.
Diagnostic Aids
• Poor connections or a damaged harness - Inspect
the harness connections for: backed out terminals,
imprope, mating or damaged terminals. Also check
for open circuit, and short to battery.
6E1-232 DRIVEABILITY AND EMISSIONS
DTC (Flash DTC = 92)
Tacho Out High Error
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 OFF.
2. Check for a faulty connection or damaged terminals at
the tacho meter connector.
Was a problem found?
-
Verify repair
Go to Step 3
3
Check for a faulty connection or damaged terminals at the
ECM connector.
Was a problem found?
-
Verify repair
Go to Step 4
4
Check for a short circuit between the meter cluster
connector and the ECM.
If a problem is found, repair the wire harness.
Is there still a problem?
-
Verify repair
Go to Step 5
5
1. Disconnect the ECM.
2. Check the ignition control circuit for a short to voltage.
Was a problem found?
-
Verify repair
Go to Step 6
6
Replace the meter cluster.
Verify repair.
Is there still a problem?
-
Go to Step 8
Refer to CKP
Sensor Signal
Incorrect
7
1. Disconnect the ECM and CKP sensor.
2. Check for a short to ground in the 58X reference circuit
between the CKP sensor connector and the ECM
harness connector.
3. If a problem is found, repair as necessary.
Was a problem found?
-
Verify repair
Go to Step 8
8
1. Reconnect the ECM and CKP sensor.
2. Connect a Digital Voltmeter (DVM) to measure voltage
on the 58X reference circuit at the ECM connector.
3. Observe the voltage while cranking the engine.
Is the voltage near the specified value?
2.5V
Go to Step 11
Go to Step 9
9
Check the connections at the CKP sensor and replace the
terminals if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 10
10
Replace the CKP sensor.
Is the action complete?
-
Verify repair
-
11
Check connections at the ECM and replace the terminals
if necessary.
Did any terminals require replacement?
-
Verify repair
Go to Step 12
12
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
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