DTC Readout With Impulse Counter Scan Tool

Diagnostic Trouble Code (DTC) Readout With Impulse Counter Scan Tool

Malfunctions which occur while starting or with the engine running are recorded by a malfunction counter. Malfunctions are assigned a specific value according to malfunction severity (e.g. hot wire MAF sensor 128, ECT sensor 32). The malfunction counter counts in stages up to a threshold value of 255. After reaching the threshold value of 128, intermittent malfunctions are stored into memory after switching off the ignition. Malfunctions which affect engine operation (greater than or equal to 128) are immediately stored into DTC memory by the malfunction counter after switching off the ignition.

If a malfunction is no longer present during a subsequent engine start or engine operation, the total value recorded by the malfunction counter is reduced by 1 every time the engine is switched off. This procedure repeats itself until the malfunction counter is cleared.

Stored malfunctions (DTC's) can be read with the impulse counter scan tool at the data link connector (X11/4).

The DTC memory readout must be performed with the engine OFF and the ignition switched ON.

Malfunctions occurring in the following areas are stored immediately:
- Cam position (CMP) sensor,
- Hot-wire MAF sensor,
- Injectors.

A malfunction of the following is stored after more than 2 trips:
- Speed signal (TN) (input).

The memory remains active even if the vehicle's battery is disconnected.

DTC's can be read with the impulse counter scan tool. Numbers ranging from 1 to 32 may appear on the display of the impulse counter scan tool. The number 1 indicates: No DTC recognized in system.

All further numbers refer to a particular malfunction source. If there are multiple system malfunctions, the malfunction assigned with the lowest number will be displayed first.

If the DTC number indicated first reappears after more than two DTC readouts, then no further malfunctions are stored in the system's memory. After eliminating all malfunctions, they must be cleared individually and the ignition must be switched off for a minimum of 15 seconds.

In case of engine running complaints, the DTC memory must be read and the malfunction must be eliminated before proceeding with any additional repairs.

Caution! The DTC's of both LH-SFI control modules (N3/2 and N3/3) must be read. Indicated DTC's in the left or right cylinder banks, if any, should be checked with the socket box tester.