DME 7.2

P1570
39 Immobilizer - Signal Implausible

P1571
39 Immobilizer - Open Circuit/No Signal

Function
When the engine is first started up or after a Motronic reset, the DME control module communicates with the alarm system control module. If this communication takes place correctly, the engine can be started. If the communication is disturbed, the engine cannot be started. The starter is not triggered

Diagnosis conditions
- Start condition
- Motronic reset

Wiring Diagram:

Diagnosis Procedure:

1 Check status of alarm system or immobilizer.

1. Connect and switch on Porsche System Tester 2.
2. Select vehicle type 996.
3. Select Alarm system or Immobilizer.
4. Select Input signals.
5. Select Immobilizer.
6. Read out status.


NOTE: If the engine is not started, the immobilizer locks again after 30 sec. (status "Immobilizer active"). If necessary, switch ignition off and on again.


2 Check current path of immobilizer.

1. Read out fault memory of alarm system or immobilizer control module.
If faults concerning the immobilizer are stored in the memory (teaching Transponder key, status wire, signal converter, etc.), these must be corrected first.

3 Check status of DME.

1. Connect and switch on Porsche System Tester 2.
2. Select vehicle type 996.
3. Select DME.
4. Select Input signals.
5. Select Immobilizer.
6. Read out status.


NOTE: If the engine is not started, the immobilizer locks again after 120 sec. (status "immobilizer active") If necessary, switch ignition off and on again.


4 Check signal wire for continuity.

1. Remove connector I of alarm system control module.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect ohmmeter to special tool 9637, pin I/3, and to alarm system connector I/23.
Display: 0 - 5 ohms

If infinity ohms is displayed, remove connector X 2/3.

4. Connect ohmmeter to connector X 2/3, pin 6, on sleeve side, and to special tool 9637, pin 1/3.
Display: 0 - 5 ohms

If infinity ohms is displayed, repair wiring harness.

5. Connect ohmmeter to connector X 2/3, pin 6, on pin side, and to alarm control module connector I, pin 23.
Display: 0 - 5 ohms

If infinity ohms is displayed, repair wiring harness.

5 Check signal wire for short circuit to ground.

1. Remove connector I of alarm system control module.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect ohmmeter to special tool 9637, pin I/3, and ground.
Display: infinity ohms

If 0 - 5 ohms is displayed, check wiring harness for chafing and pinching damage.

6 Check signal wire for short circuit to B+.

1. Remove connector I of alarm system control module.
2. Connect special tool 9637 to wiring harness (DME control module connector).
3. Connect voltmeter to special tool 9637, pin I/3, and ground.
Display: 0 V

If battery voltage is displayed, check wiring harness for chafing and pinching damage.