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) 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. The MIL may be turned off by the ECM/PCM if the problem that originally caused the MIL to be illuminated is a intermittent one.

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 ECM/PCMs) this can sometimes mean something works, but not the way it's supposed to.

How to Use the HDS (Honda Diagnostic System)


If the MIL (Malfunction Indicator Lamp) has come on


1.Start the engine and check the MIL (A).

 

2.If the MIL stays on, connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.

 

3.Turn the ignition switch ON (II).

4.Check the diagnostic trouble code (DTC) and note it. Also check the freeze data. Refer to the DTC Troubleshooting and begin the appropriate troubleshooting procedure.

NOTE:
  • Freeze data indicates the engine conditions when the first malfunction, misfire, or fuel trim malfunction was detected.
  • The HDS can read the DTC, freeze data, current data, and other engine control module (ECM)/powertrain control module (PCM) date.
  • For specific operations, refer to the user's manual that came with the HDS.

5.If no DTCs are found, go to MIL troubleshooting.

If the MIL did not stay on

If the MIL did not stay on but there is a driveability problem, do the symptom troubleshooting.

If you can't duplicate the DTC

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

HDS Clear Command


The ECM/PCM stores various specific data to correct the system even when there is no electrical power such as the battery negative terminal or No. 2 ENG (30 A) fuse are disconnected. Stored data based on failed parts should be cleared by using the ‘‘CLEAR COMMAND'' of the HDS, if parts are replaced.

The HDS has three kinds of clear command to meet this purpose. They are DTC clear, ECM/PCM clear, and CKP pattern clear. DTC clear command erases all stored DTC codes and freeze data. This must be done with the HDS after reproducing the DTC during troubleshooting in this service manual.
ECM/PCM clear command erases all stored DTC codes, freeze data, and all specific data to correct the system except CKP pattern. If the CKP pattern data in ECM/PCM was cleared, you must do the CKP pattern learn procedure. The CKP pattern clear command erases only CKP pattern data. This command is for the repair of a misfire or CKP sensor.

DTC CLEAR


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

2.Turn the ignition switch OFF.

3.Turn the ignition switch ON (II). Wait for 30 seconds.

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

ECM/PCM RESET


This command clears stored specific data from each vehicle such as DTCs freeze data. It does not clear CKP PATTERN data.

1.Reset the ECM/PCM with the HDS while the engine is stopped.

2.Turn the ignition switch OFF.

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

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

5.Do the ECM/PCM idle learn procedure.

CKP PATTERN CLEAR/CKP Pattern Learn


NOTE: The ECT needs to be at 80 °C (176 °F) or higher.

1.Clear the CKP pattern with the HDS while the engine is stopped.

2.Turn the ignition switch OFF.

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

4.Test-drive the vehicle on a level road: Decelerate (with the throttle fully closed) from engine speed of 2,500 rpm to 1,000 rpm with the A/T in 2 position, or the M/T in 2nd or 3rd gear.

5.Stop the vehicle. Do not turn the ignition switch OFF.

6.Select the ALL DATA LIST in the DATA LIST MENU of the HDS.

7.Check the status of PULSER F/B LEARN. If it is set to NG, the enable criteria was probably not met; repeat the procedure from the beginning.

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


1.Reset the ECM/PCM with the HDS.

2.Do the ECM/PCM idle learn procedure.

3.Turn the ignition switch OFF.

4.Disconnect the HDS from the DLC.

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

How to Remove the ECM/PCM for Testing


If the inspection for a trouble code requires voltage or resistance checks at the ECM/PCM connectors, remove the ECM/PCM and test it:

1.Jump the SCS line with the HDS.

2.Remove the passenger's dashboard under cover, and the glove box.

3.Cut the plastic cross brace in the glove box opening with diagonal cutters in the area shown. Remove and discard the plastic cross brace (A).

 

4.Remove the relay holders (B) from the grove box frame.

5.Remove the gray 20P ECM/PCM wire harness connector (A) from the ECM/PCM mounting bracket (B). Remove the ECM/PCM mounting bolt (C) and the bracket.

 

6.Remove the nuts (D), then remove the ECM/ PCM (E).

7.Install the ECM/PCM in the reverse order of removal.

8.Open the SCS line with the HDS.

How to Troubleshoot Circuits at the ECM/PCM


1.Gently slide the sharp tester probe (A) into the connector from wire side until it touches the end of the wire terminal.

 

2.If you cannot get to the wire side of the connector or the wire side is sealed (A), disconnect the connector and probe the terminals (B) from the terminal side. Do not force the probe into the connector.



Do not puncture the insulation on a wire.Punctures can cause poor or intermittent electrical connections.

 


ECM/PCM 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/PCM in a troubleshooting procedure. Update the ECM/PCM only if the ECM/PCM does not have the latest software loaded.

NOTE: Do not turn the ignition switch OFF while updating the ECM/PCM. If you turn the ignition switch OFF before completion, the ECM/PCM can be damaged.

How to Update the ECM/PCM


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/PCM update procedure as described on the HIM label and in the ECM/PCM update system.

4.Do the ECM/PCM idle learn procedure.

5.Clear the CKP pattern with the HDS while the engine stopped.

How to Substitute the ECM/PCM


1.Remove the ECM/PCM from the vehicle.

2.Install a known-good ECM/PCM.

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

4.After completing your tests, install the original ECM/PCM and rewrite the immobilizer code with the ECM/PCM 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: