Reading and Clearing Diagnostic Trouble Codes
Control System DTCs
How to Troubleshoot the 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 terminals at all connectors related to the circuit that you are troubleshooting. If the MIL was on but then went off, the original problem may have been intermittent.
Service Information
Periodically, new ECM software or new service procedures may become available. Always check online for the latest software or service information related to the DTCs or symptoms 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 Use the HDS (Honda Diagnostic System)
1. 1. Start the engine, and check the MIL (A).
NOTE: If the ignition switch is turned to ON (II), and the engine is not started, the MIL stays on for 15-20 seconds.
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 to ON (II).
4. Make sure the HDS communicates with the ECM and other vehicle systems. If it does not, go to the DLC circuit troubleshooting Testing and Inspection.
5. Check the diagnostic trouble code (DTC) and note it. Also check the freeze data and/or on-board snapshot data, and download any data found. Then refer to the indicated DTC's 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, the freeze data, the on-board snapshot, the current data, and other engine control module (ECM) data.
* For specific operations, refer to the user's manual that came with the HDS.
6. If no DTCs are found, go to the MIL circuit 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 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 needlessly replaced ECM.
HDS Clear Command
The ECM stores various specific data to correct the system even if there is no electrical power such as when the battery negative terminal or No. A21 (15 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 commands to meet this purpose. They are DTC clear, ECM reset, and CKP pattern clear. The DTC clear command erases all stored DTC codes, freeze data, on-board snapshot, and readiness codes. This must be done with the HDS after reproducing the DTC during troubleshooting. The ECM reset command erases all stored DTC codes, freeze data, on-board snapshot, readiness codes, and all specific data to correct the system except CKP pattern. If the CKP pattern data in the ECM was cleared, you must do the CKP pattern learn procedure. The CKP pattern clear command erases only CKP pattern data. This command is for repair of a misfire or the CKP sensor.
Scan Tool Clear Command
If you are using a generic scan tool to clear commands, be aware that there is only one setting for clearing the ECM, and it clears all commands at the same time (CKP pattern learn, idle learn, readiness codes, freeze data, on-board snapshot, and DTCs). After you clear all commands, you then need to do these procedures, in this order: ECM idle learn procedure; CKP pattern learn procedure.
DTC Clear
1. Clear the DTC with the HDS while the engine is stopped.
2. Turn the ignition switch to LOCK (0).
3. Turn the ignition switch to ON (II), and wait 30 seconds.
4. Turn the ignition switch to LOCK (0), and disconnect the HDS from the DLC.
ECM Reset
1. Reset the ECM with the HDS while the engine is stopped.
2. Turn the ignition switch to LOCK (0).
3. Turn the ignition switch to ON (II), and wait 30 seconds.
4. Turn the ignition switch to LOCK (0), and disconnect the HDS from the DLC.
5. Do the ECM idle learn procedure. ECM/PCM Idle Learn Procedure
How to End a Troubleshooting Session (required after any troubleshooting)
1. Reset the ECM with the HDS.
2. Do the ECM idle learn procedure. ECM/PCM Idle Learn Procedure
3. Turn the ignition switch to LOCK (0).
4. Disconnect the HDS from the DLC.
NOTE: The ECM is part of the immobilizer system. If you replace the ECM, you must use the HDS to instruct the new ECM and the immobilizer- keyless control unit to recognize each other's unique serial code.
How to Troubleshoot Circuits at the ECM Connectors
NOTE: The ECM stays on for about 60 minutes after the ignition switch is turned to LOCK (0). Jumping the SCS line after turning the ignition switch to LOCK (0) cancels this function. Disconnecting the ECM during this function, without jumping the SCS line first, can damage the ECM.
1. Jump the SCS line with the HDS.
2. Remove the cover (A).
3. Disconnect ECM connectors A, B, and C.
NOTE: ECM connectors A, B, and C have symbols (A=(square), B=(triangle), C=(circle)) embossed on them for identification.
4. When diagnosis/troubleshooting is done at the ECM connectors, use the terminal test port (A) above the terminal you need to check.
5. Connect one side of the patch cord terminals (A) to a commercially available digital multimeter (B), and connect the other side of the terminal (C) to a commercially available banana jack (Pomona Electronics Tool No. 3563 or equivalent) (D).
6. Gently contact the pin probe (male) at the terminal test port from the terminal side. Do not force the tips into the terminals.
NOTICE:
* For accurate results, always use the pin probe (male).
* To prevent damage to the connector terminals, do not insert test equipment probes, paper clips, or other substitutes as they can damage the terminals. Damaged terminals cause a poor connection and an incorrect measurement.
* Do not puncture the insulation on a wire. Punctures can cause or eventually lead to poor or intermittent electrical connections.
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 repair was successfully completed. The results of diagnostic tests for the DTC are displayed as:
* PASSED: The on board diagnosis is successfully finished.
* FAILED: The on board diagnosis has finished but failed.
* EXECUTING: The vehicle is in enable criteria conditions of the DTC, and the on board diagnosis is running.
* NOT COMPLETED: The on board diagnosis was running but is out of the enable conditions of the DTC.
* OUT OF CONDITION: The vehicle has stayed out of the enable conditions of the DTC.