How to Troubleshoot Fuel and Emissions Systems

Intermittent Failures


The term ‘'intermittent failure'' means a system may have had a failure, but it checks OK now. If the malfunction indicator lamp (MIL) or the glow plug indicator on the dash does not come on, check for poor connections or loose pins at all connectors related to the circuit that you are troubleshooting.

Opens and Shorts


‘'Open'' and ‘'Short'' are common electrical terms. An open is a break in a wire or at a connection. A short is an accidental connection of a wire to ground or to another wire. In simple electronics, this usually means something won't work at all. With complex electronics (such as ECMs) this can sometimes mean something works, but not the way it's supposed to.

How to Check for DTCs with the HDS


When the ECM senses a malfunction in the system, the MIL (A) or the glow plug indicator (B) in the gauge assembly will come on.

 

When the HDS is connected to the data link connector (DLC) (A) (located under the driver's side of the dashboard), it will indicate the diagnostic trouble code (DTC) when the ignition switch is turned ON (II).

 

If the MIL or the glow plug indicator has been reported on, or if a drivability problem is suspected, follow this procedure:

1.Connect the HDS to the DLC (see the HDS user's manual for specific instructions).

2.Turn the ignition switch ON (II), select DIESEL system and observe the DTC in the DTC MENU on the screen.

3.Record all DTCs, and freeze data.

4.Do the troubleshooting for the indicated DTCs.

5.If you can't check the DTC and the MIL stays on, do the MIL circuit troubleshooting.

6.If you can't check the DTC and the glow plug indicator stays on, do the glow plug indicator circuit troubleshooting.

If the MIL and/or the glow plug indicator does not come on

If the MIL and/or the glow plug indicator does not come on but there is a drivability problem, do the symptom troubleshooting.

If you can't duplicate the DTC

Some of the troubleshooting requires you to reset the ECM and try to duplicate the DTC. If the problem is intermittent and you can't duplicate the DTC, do not continue through the procedure. To do so will only result in confusion and possibly, a needless replaced ECM.

HDS Clear Command


The inside ECM stores various specific data to correct the system even when there is no electrical power such as the battery negative terminal or No. 8 FI ECU (ECM) (15 A) fuse are disconnected. But stored data based on failure parts should be cleared by using the ‘‘CLEAR COMMAND'' of the HDS, if parts are replaced.

HDS has three kings of clear command to meet the purpose. They are DTC clear, ECM clear. DTC clear command erases all stored DTC codes and Freeze Data. This must be done with the HDS after reproducing DTC during troubleshooting. ECM clear command erases all stored DTC codes, Freeze Data and all specific data to correct the system.

DTC Clear


1.Clear the DTC with the HDS with the engine stopped.

2.Turn the ignition switch OFF.

3.Turn the ignition switch ON (II), and wait 30 seconds.

4.Turn the ignition switch OFF, and disconnect the HDS from the DLC.

ECM Reset


This command clears stored specific data from each vehicle such as DTC and Freeze Data.

1.Reset the ECM with the HDS with the engine stopped.

2.Turn the ignition switch OFF.

3.Turn the ignition switch ON (II), and wait 30 seconds.

4.Turn the ignition switch OFF, and disconnect the HDS from the DLC.

How to End a Troubleshooting Session (required after any troubleshooting)


1.Reset the ECM with the HDS.

2.Turn the ignition switch OFF.

3.Disconnect the HDS from the DLC.

NOTE: The ECM is part of the immobilizer system. If you replace the ECM, it will have a different immobilizer code. In order for the engine to start, you must rewrite the immobililzer code with the HDS.

How to Remove the ECM for Testing


If DTC troubleshooting requires voltage or resistance checks at the ECM connectors, remove the ECM and test it:

1.Turn the ignition switch OFF, and wait 30 seconds.

2.Disconnect the ECM connectors (A).

 

3.Remove the bracket (B), then remove the ECM (C).

4.Install the ECM in the reverse order of removal.

How to Troubleshoot Circuits


Special Tools Required
ECM test probe set (  070AJ-RBD0200)



1.Gently slide the tester probe into the connector hole (A).

 

ECM Updating and Substitution for Testing


Special Tools Required
Honda interface module ( (HIM) EQS05A35570)



Use this procedure when you have to substitute a known-good ECM in a troubleshooting procedure. Update the ECM only if the ECM does not have the latest software loaded.

NOTE:

1.Turn the ignition switch ON (II). Do not start the engine.

2.Connect the HDS or the Honda interface module (HIM) to the data link connector (DLC) (A) located under the driver's side of the dashboard.

 

3.Do the ECM update procedure as described on the HIM label and in the ECM update system.

How to Substitute the ECM


1.Remove the ECM from the vehicle.

2.Install a known-good ECM.

3.Rewrite the immobilizer code with the ECM replacement procedure in the HDS; it allows you to start the engine.

4.After completing your tests, install the original ECM and rewrite the immobilizer code with the ECM replacement procedure in the HDS.

OBD Status


The OBD Status shows the current system status of each DTC and all of the parameters. This function is used to see if the technician's repair was successfully finished. The results of diagnostic tests for the DTC are displayed as: