Isuzu engine C22NE / 22LE / 20LE. Manual — part 84
DRIVEABILITY AND EMISSIONS 6E1-165
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 18)
DIGITALLY CONTROLED SIGNAL TO NOISE ENHANCEMENT FILTER FAILURE
Circuit Description
The knock sensor (KS) system is used to detect
engine detonation. The knock sensor produced an AC
voltage signal. The knock sensor sends this signal to
the ECM. The amplitude and the frequency of the AC
voltage signal depends upon the knock level being
detected. The ECM will then retard the spark timing
based on the signals from the Knock Sensor.
This code detects a digitally controlled signal to noise
enhancement filter failure. Then the DTC 18 will set.
Conditions for Setting the DTC
• ECM powered up, Engine running, Electronic spark
control enabled and Engine rpm is greater than 96
rpm.
• Malfunction 16 is not triggered.
Action Taken When the DTC Sets
• The Malfunction Indicator Lamp (MIL) will illuminate
the second time the fault is detected.
• The ECM will use a calculated spark retard value in
order to minimize the knock during the conditions
when the knock is likely to occur. The calculated
value will vary based on the engine speed and load.
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.
Diagnostic Aids
Correct any abnormal engine noise before using the
diagnostic table.
Check for an open ignition feed circuit.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Table.
2. If the conditions for the test as described above are
met, a Diagnostic Trouble Code 18 will set and MIL
will illuminate.
6E1-166 DRIVEABILITY AND EMISSIONS
5. Any circuitry, that is suspected as causing the
complaint, should be thoroughly checked for
backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals,
poor terminal to wiring connections or physical
damage to the wiring harness.
9. If the KS module was previously replaced and the
Diagnostic Trouble Code resets, a malfunctioning
ECM is indicated.
DTC (Flash DTC = 18)
Digitally Controlled Signal To Noise Enhancement Filter Failure
Step
Action
Value(s)
Yes
No
1
Was the On-Board Diagnostic(OBD) System Check
performed?
-
Go to Step2
Go to
Powertrain
OBD System
Check
2
1. Operate the engine within the conditions specified in
the diagnostic support Conditions for Setting the
Diagnostic Trouble Code.
2. Using a Scan Tool, monitor the Specific DTC
information for DTC 18.
3. Observe the test results.
Does the Scan Tool indicate the DTC 18.
-
Go to Step 3
Go to
Diagnostic
Aids
3
1. Turn ON the ignition with the engine leaving OFF.
2. Disconnect the KS electrical connector.
3. Using a Digital Voltmeter (DVM), measure the voltage
between the KS signal circuit at the knock sensor
harness connectors and ground.
Is the voltage at the specified value?
Approx.5.0V
Go to Step 4
Go to Step 7
4
Measure the resistance of the KS sensor by connecting
the between the KS sensor terminal and the engine block.
Is the resistance of the KS sensor near the specified
value?
100K OHMS
Go to Step 5
Go to Step 8
5
1. Check the KS signal circuit for a poor terminal
connection at the knock sensor.
2. If a problem is found, repair as necessary. Refer to
Wiring Repairs in Engine Electrical.
Was a problem found?
-
Go to Step 6
Go to Step 8
DRIVEABILITY AND EMISSIONS 6E1-167
DTC (Flash DTC = 18)
Digitally Controlled Signal To Noise Enhancement Filter Failure (Cont’d)
Step
Action
Value(s)
Yes
No
6
1. Re-Connect the KS Sensor in order to monitor the
voltage between the KS sensor terminal and the engine
ground.
2. Tap on the engine lift bracket, near the KS Sensor,
while observing the signal indicated on the Scan Tool.
Is any signal indicated on the while tapping on the engine
lift bracket?
-
Go to Step 10
Go to Step 7
7
1. Turn OFF the ignition.
2. Disconnect the ECM.
3. Turn ON the ignition.
4. Check the KS signal circuit between the ECM and the
KS sensor connector for an open, a short to voltage, or
a short to ground.
5. If a wiring problem is found, repair as necessary.
Was a problem found?
-
Go to Step 10
Go to Step 9
8
Replace the KS Sensor. Refer to Knock Sensor.
Is action complete?
-
Go to Step 10
-
9
Replace the EPROM or ECM.
Note) Refer to 6E1-243.
Is the action complete?
-
Go to Step 10
-
10
1. Using the Scan Tool, select the DTC and the Clear
Info.
2. Start the Engine.
3. Idle at the normal operating temperature.
4. Select Specific DTC.
5. Enter the DTC number which was set.
6. Operate the vehicle within the conditions for setting this
DTC as specified in the supporting text.
Does the Scan Tool indicate that this diagnostic ran and
passed?
-
Go to Step 11
Go to Step 2
11
Using the Scan Tool, select the Capture Info and the
Review Info.
Are any DTC displayed that have not been diagnosed?
-
Go to the
applicable
Diagnostic
Trouble Code
table
System OK
6E1-168 DRIVEABILITY AND EMISSIONS
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