On-Board Diagnostic System

The A-604 ultradrive transaxle system is monitored by the A~604 controller. The A-604 controller monitors critical input and output circuits within the A-604 Ultradrive Transaxle system, making sure they are operating correctly.

Some circuits are tested continuously; others are checked only under certain conditions.

Each circuit monitored by the A-604 controller has a corresponding fault message assigned to it. Refer to "System Fault Messages" later in this section for a list and definition of the fault messages.

- If the on~board diagnostic system senses that one of the circuits is malfunctioning, it stores the corresponding fault message in memory.

- If the malfunction goes away after the fault is stored, the fault message will be erased after 75 key cycles.


SYSTEM FAULT MESSAGES/CODES

Fault codes are two.digit numbers that identify which circuit is malfunctioning. A fault code can be set for hydraulic and mechanical reasons as well as for electrical problems. In most cases, fault codes do not pinpoint which specific component is defective.

Hard Faults

Any fault code that comes back within 3 cycles of the ignition key is a "hard' fault. This means that the defect is there every time the controller checks that circuit.

Soft Faults

A "soft" fault is one that occurs intermittently; it is not there every time the controller checks the circuit. Most soft faults are caused by wiring or connector problems. Defects that come and go like this are the most difficult to diagnose; they must be looked for under the specific conditions that cause them.

Reset Counter

The reset counter counts the number of times the vehicle has been started since faults were last set, erased, or the battery was disconnected. The reset counter will count up to 255 starts.

When there are no faults stored in memory, the DRBII will display "NO FAULTS DETECTED" and the reset counter will show "RESET COUNT = XXX".

The number of starts helps determine whether a fault is hard or soft.

- If the reset counter reads less than 3, the fault is a hard fault.

- If the reset counter reads 3 or more, the fault is a soft or intermittent fault. This means that the engine has been started several times without the fault reoccurring.