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Questions and Answers

Honda Civic MIL And D4 Lights

Q. Help! I brought my 1998 Honda Civic DX home from the dealership to have the ignition components replaced. They also told me the exhaust manifold was cracked. I fixed this myself and replaced the two oxygen sensors. Problem is ever since I drove it off the lot the light that indicates the car is in Drive has been blinking.

Honda Civic MIL And D4 Lights On

Also the Check Engine Light (MIL) is on, which wasn't occurring before I brought it in. They told me they had no idea why the light would be blinking and to fix the MIL they would have to shut it off with the scanner. I disagree. Why is the Drive light blinking and I'm sure there is a way to clear the ECU memory at home.


A. If the MIL is on, then the computer has detected a malfunction. And as long as the light is on, the malfunction is present. If the malfunction has cleared, the MIL would go out but retain a Diagnostic Trouble Code (DTC) in memory. You will need a scan tool to find out what the code is. Once we know that, we can trace the problem and fix it.

The following procedure will reset the ECM/PCM without a scan tool.

Honda Civic MIL And D4 Lights
Turn the ignition switch OFF, and remove the No. 13 CLOCK BACKUP fuse (7.5 amp) (A) from the passenger's under-dash fuse/relay box (B) for 10 seconds

When the PCM senses an abnormality in the transmission input or output ystems, the D4 indicator light in the gauge assembly will blink. When the 16P Data Link Connector (DLC) (located next to the driver's side kick panel) is connected to the SCS Service Connector (DLC), the D4 indicator light will blink the Diagnostic Trouble Code (DTC) when the ignition switch is turned ON.

Honda Civic MIL And D4 Lights

If the D4 indicator light and the MIL come on at the same time, follow this procedure:

  • Record the DTCs.
  • Check the fuel/emission system indicated by the DTC.
  • Get the radio anti-theft code.
  • Reset the memory by removing the BACK UP fuse in the passenger's under-dash fuse/relay box for more than 10 seconds.
  • Drive the vehicle for several minutes at a speed over 30 mph, and then recheck the DTCs.
  • Re-enter the radio code and reset the clock.

Once we know that code we can start to locate the problem.

Additional Information provided courtesy of ALLDATA

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