Without Scan Tool

DIAGNOSTIC CODE INTERPRETATION
The Transmission Control Module (TCM) monitors operation of the transmission control system. Some components are monitored continuously, others only during specified operating conditions. When the TCM detects a malfunction lasting longer than a specified period of time the TCM will generate an error code that can be detected at the [1][2]diagnostic connector.

There are 26 diagnostic items (including normal operation) plus 7 fail safe items that will generate diagnostic codes. The malfunction codes are erased when the vehicle battery is disconnected for more than ten seconds.

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. A maximum of up to 10 fault codes can be stored in the control module's memory. If the number of stored codes exceeds 10, previously stored codes will be erased, beginning with the oldest code.

If the fail-safe system is activated, the transaxle will be locked in one forward gear while in any of the forward gear positions. This is provided so that the customer can "limp" the vehicle to a repair facility without causing further damage to the transmission.

Voltmeter Output Waveform:

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 1.5 seconds. This will represent one module of ten. There will be approximately a two second delay and then the needle will deflect three times for approximately 0.5 seconds with 0.5 second delay between deflections. This will represent three modules of one.
Code 24
The needle will deflect two times for approximately 1.5 seconds each with approximately 0.5 second delay between deflections. This will represent two modules of ten. There will be approximately a two second delay and then the needle will deflect four times for approximately 0.5 seconds with 0.5 second delay between deflections. This will represent four modules of one.

Reading Codes With A Voltmeter:

READING DIAGNOSTIC TROUBLE CODES
1. Connect an analog voltmeter to the ground and the transmission self diagnosis output pin of the [1][2]diagnostic connector.
2. Set the ignition switch to "ON".
3. Note the pattern of pulses displayed on the voltmeter. If the voltmeter indicates a steady voltage (either 0 volts or 12 volts) the TCM has failed.
4. Refer to the diagnostic codes chart to determine which device is causing the malfunction code.
5. Test and repair the offending components as necessary.
6. Clear the malfunction codes by disconnecting the vehicle battery negative terminal for ten seconds or longer.
7. Road test the vehicle and recheck for newly stored diagnostic codes.
8. After the cause of a failure code has been detected and corrected the diagnostic code memory of the TCM should be cleared by disconnecting the vehicle battery for 10 seconds or more.