Dtc P1621 (Flash Code 54) - Isuzu 2008MY N Series Workshop Manual

1A-250 Engine Control System (4HK1)

DTC P1621 (Flash Code 54)

Circuit Description
This diagnostic applies to internal microprocessor
integrity conditions within the ECM.
Condition for Running the DTC
• The ignition switch is ON.
Condition for Setting the DTC
• The ECM detects that the calculated checksum
does not agree with the electrically erasable &
programmable read only memory (EEPROM)
internal registered checksum.
Circuit/ System Testing DTC P1621
Step
Did you perform the Diagnostic System Check
1
- Engine Controls?
1. Ensure that all tool connections are secure.
2. Ensure
operating correctly.
3. Install a scan tool.
2
4. Turn OFF the ignition for 30 seconds.
5. Turn ON the ignition, with the engine OFF.
6. Monitor the DTC Information with a scan tool.
Does the DTC fail this ignition?
Important:
programmed and learned.
3
Replace the ECM. Refer to ECM Replacement.
Did you complete the replacement?
1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for
4 Running the DTC. You may also operate the
vehicle
observed from the Freeze Frame/ Failure
Records.
Did the DTC fail this ignition?
Observe the DTC Information with a scan tool.
5
Are there any DTCs that you have not
diagnosed?
Action
that programming equipment
Replacement ECM
within the conditions
Action Taken When the DTC Sets
• The ECM illuminates MIL when the diagnostic runs
and fails. Refer to DTC Type Definitions for Action
Taken When the DTC Sets - Type A.
Condition for Clearing the DTC
• Refer to DTC Type Definitions for Condition for
Clearing the MIL/ DTC - Type A.
Value(s)
—
is
—
must be
—
—
that you
—
Yes
Go to Diagnostic
System Check -
Go to Step 2 Engine Controls
Go to Step 3 Go to Step 4
Go to Step 4
Go to Step 3 Go to Step 5
Go to DTC List
No
—
System OK