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 wires 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. In complex electronics (like ECM's/PCM's) this can sometimes mean something works, but not the way it's supposed to.

How to Use the Honda PGM Tester or a Scan Tool

If the MIL has come on

1.Start the engine and check the MIL.


2.If the MIL stays on, connect the Honda PGM Tester (A) or a scan tool to the Data Link Connector (DLC) (B) 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 frame data. Refer to the DTC Troubleshooting Index and begin the appropriate troubleshooting procedure.


If the MIL did not come on

If the MIL did not come 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.

How to Reset the ECM/PCM

You can reset the ECM/PCM in either of 2 ways:


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

1.Reset the ECM/PCM as described above.

2.Turn the ignition switch OFF.

3.Disconnect the scan tool or Honda PGM Tester 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 Honda PGM Tester.

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.Make sure you have the anti-theft code for the radio, then write down the radio station presets.

2.Disconnect the negative cable from the battery.

3.Remove the passenger's dashboard lower cover, and the glove box.

4.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).


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

6.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.


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

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

9.Reconnect the negative cable to the battery.

10.Enter the radio anti-theft code and the radio station preset then set the clock.

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.


How to Substitute the ECM/PCM

1.Disconnect the negative cable from the battery.

2.Remove the ECM/PCM from the vehicle.

3.Install a known-good ECM/PCM in the vehicle.

4.Reconnect the negative cable to the battery.

5.Rewrite the immobilizer code with the ECM/PCM replacement procedure on the Honda PGM Tester. It allows you to start the engine.

6.After completing your tests, reinstall the original ECM/PCM and rewrite the immobilizer code with the ECM/PCM replacement procedure on the Honda PGM Tester again.