Without Scan Tool

DIAGNOSTIC CODE INTERPRETATION

The Engine Control Unit (ECU) monitors operation of the emission control system. Some components are monitored continuously, others only during specified operating conditions. When the ECU detects a malfunction lasting longer than a specified period of time the ECU will generate an error code that can be detected at the diagnostic connector.


There are fifteen diagnostic items (including normal operation) that will generate diagnostic codes. The malfunction codes are erased when the vehicle battery is disconnected for more than ten seconds.
NOTE: If the oxygen sensor is disconnected during engine operation for testing purposes a code will be stored and must be cleared after the test is complete.
To test for oxygen sensor codes drive the vehicle a significant distance and check for diagnostic codes before turning the ignition off. Do not however disconnect the battery with the ignition on or the engine running as permanent damage to the vehicle electronic components may result.
If multiple malfunctions occur the diagnostic codes will be sent sequentially beginning with the lowest number code in ascending order with a 2 second pause between each code.
The Voltmeter needle will deflect for a particular duration and a certain number of times.
FOR EXAMPLE:
Code 13
The needle will deflect one time for approximately 0.5 second. This will represent one unit of ten. There will be approximately a one second delay and then the needle will deflect three times for approximately 0.2 seconds with 0.1 second delay between deflections. This will represent three units of one.
Code 23
The needle will deflect two times for approximately 0.5 second with approximately 0.3 second delay between deflections. This will represent two units of ten. There will be approximately a one second delay and then the needle will deflect three times for approximately 0.2 seconds with 0.1 second delay between deflections. This will represent three units of one.







1. Connect an analog Voltmeter between the on-board diagnostic output terminal of the data link connector and ground terminal.
2. Turn on the ignition switch.
3. Read the on-board diagnostic output pattern from the Voltmeter and record it.
4. Referring to the diagnostic chart, repair the faulty part.
5. Erase the diagnostic trouble code.