P1720

Symptom: "CHECK ACS" warning lamp on. If the gear lever sensor is faulty, difficulty will be experienced in changing gear during heavy engine braking or on a light throttle.

P1720

-	Unplug the gear selector movement sensor's 4-pin connector. It is located under the gear lever gaiter and secured in a holder by means of a screw. Note that only three pins are used.

-	Turn the ignition switch to the ON position.

-	Take voltage readings on the connector contacts as follows:

•

Across pin 1 and a good grounding point. A reading of between 7.5 V and B+ should be obtained.

•

Across pins 1 and 2. A reading of between 7.5 V and B+ should be obtained.

All readings OK?

yes

Continue with point 2.

no

Repair or replace the lead in question and proceed to point 3.

2 Check the sensor input

-	Select the "READ FUNCTIONS" menu and "GEAR SELECTOR MOVEMENT SENSOR" in the Scan tool diagnostics instrument.

-	Connect a jumper lead in the sensor's female connector across pins 2 and 3. The Scan tool diagnostics instrument should show about 0 V.

-	Then connect a jumper lead across pins 1 and 3. The Scan tool diagnostics instrument show a reading of about 5 V.

All readings OK?

yes

Change the gear selector movement sensor, see . Then continue with point 3.

no

Repair or replace the lead in question and proceed to point 3.

3 Final check

-	Clear the diagnostic trouble code.

-	Perform a drive cycle by driving the car at varying engine rpm and loads for 5 minutes. Change gear frequently.

-	Check whether the diagnostic trouble code has recurred.

Has the diagnostic trouble code recurred?

yes

Continue as described in the section "Before replacing a control module", see .

no

The steps taken to rectify the fault were correct.