Description of On-Board Diagnostics

"Check Trans" Check





1. Indicator it is ON during 2 seconds at ignition (or when the engine is cranked) but it is OFF after the engine starts. The indicator is working normally GO TO DIAGNOSTIC CHECK. With Generic Scan Tool





Normal

2. Indicator it is flashing and the flash is 0.8 seconds ON and 0.8 seconds OFF always when ignition is on (engine cranked or not). This means that there is a malfunction. GO TO DIAGNOSTIC CHECK.





Abnormal

3. Indicator it is staying ON always when Ignition is ON.
1. This means that connection between the lamp and the PCM is shorted to ground.
2. Verify if instrument panel terminal 7 of connector B-4 is shorted to ground.
3. Verify if the PCM connector J1 (RED) terminal A14 is shorted to ground.
4. Verify that the instrument panel terminal 5 of connector B-4 is connected to battery.
5. IF problem solved: GO TO CHECK TRANS INDICATOR.
NO: Replace Powertrain Control Module (PCM).





4. Indicator it is staying OFF with the ignition ON (engine OFF).
1. This means that connection between the lamp and the PCM is shorted to battery or opened.
2. Verify if instrument panel terminal 7 of connector B-4 is shorted to battery or open.
3. Verify if the PCM connector J1 (RED) terminal A14 is shorted to battery or open.
4. Verify that the instrument panel terminal 5 of connector B-4 is connected to battery. If not, check the fuses.
5. IF problem solved: GO TO CHECK TRANS INDICATOR.
NO: Replace Powertrain Control Module (PCM).

Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) looks the same as the MIL you are already familiar with ("CHECK ENGINE" lamp). However, OBD II requires that it illuminate under a strict set of guidelines. Basically, the MIL is turned on when the PCM detects a DTC that will impact the vehicle's emissions.
The MIL is under the control of the Diagnostic Executive. The MIL will be turned on if a component or system which has an impact on vehicle emissions indicates a malfunction or fails to pass an emissions-related diagnostic test. It will stay on until the system or component passes the same test, for three consecutive trips, with no emissions-related faults.

Types Of Diagnostic Trouble Codes (DTCs)
The Diagnostic Executive classifies Diagnostic Trouble Codes (DTCs) into certain categories. Each type has different requirements to set the code, and the Diagnostic Executive will only illuminate the Malfunction Indicator Lamp (MIL) for emissions-related DTCs. DTCs fall into four categories: A, B. C, and D; only types A and B are emission-related The following descriptions define these categories:

TYPE A
Will store the DTC and turn on the MIL ("Check Engine" lamp) on the first trip in which an emission-related diagnostic test has run and reported a "test failed" to the Diagnostic Executive.

TYPE B
Will store the DTC and turn on the MIL on the second consecutive trip in which an emission-related diagnostic test has run and reported a "test failed" to the Diagnostic Executive. After one failure, the type B DTC is "armed," or prepared to store a history code and turn on the MIL if a second failure occurs. One passed test will disarm a type B DTC. Some special conditions apply to misfire and fuel trim DTCs. For a type B DTC to store and turn on the MIL, two ignition cycles are required.

TYPE C
Will store the DTC and turn on a "SERVICE" lamp ("Check Trans" lamp) on the first trip that a non-emission-related diagnostic test has run and reported a "test failed" to the Diagnostic Executive. This type of DTC will be used in future applications.

TYPE D
Will store a DTC but will not turn on the MIL on the first trip that a non-emission-related diagnostic test has run and reported a "test failed" to the Diagnostic Executive. These codes can be very helpful for vehicle service when the driver may comment about a condition, but the MIL did not turn on.