High Pressure Sensor G65

High Pressure Sensor, Checking

The following describes manual checking of High Pressure Sensor G65 using conventional measuring tools.

A guided checking procedure is also possible using the VAS 5051/5052 tester in operating mode "Guided Fault Finding".

Note:
- The presence of G65 is engine dependant. Where G65 is not used, A/C pressure switch F129 is used instead.
- Where G65 is used, its wiring circuit varies according to engine application (E.g.: some are connected to the ECM, some are not).
- Always confirm system use of either G65 or F129 and applicable wiring circuit using applicable "Engine" and "Air conditioning" wiring diagrams.






Special tools, testers and auxiliary items required
- If performing guided test, use VAS 5051/5052
- Applicable wiring diagram
- VAG 1767 Ignition tester (or equivalent device capable of duty cycle measurements)
- VAG 1594/A (or C) Connector test set
- VAG 1598 A Test box
- In cases where refrigerant system may need to be recharged, use Kent-Moore ACR (or equivalent, VAG 1885 illustrated for reference only).

Prerequisites
- Workshop temperature: 20-30 � C (68-86 � F)
- Engine at workshop temperature.

Preparation

Note:
- The following test procedure is only possible on vehicles where the G65 square wave signal to Coolant Fan Control (FC) Control Module J293 is also transmitted to the Motronic Engine Control Module (ECM). Confirm G65 circuit using wiring diagram.
- On vehicles where G65 is NOT connected to the ECM, connect green clip from VAG 1767 directly to G65 pin 2 using appropriate VAG 1594 adapter cable - 7 - . Proceed directly to checking.

- Disconnect engine harness electrical connection from Engine Control Module (ECM) - 3 - .
- Locate correct test box VAG 1598A - 4 - and adapter according to pin assignments of ECM - 3 - and connect test box to engine wiring connector/harness - 2 - .
- Connect black clip from VAG 1767 to Ground (GND) - 5 - .






- Determine applicable G65 signal input pin assignment to ECM using wiring diagram. Example: T121/61

Note:
- As G65 function primarily controls coolant fan and A/C clutch operation, the engine wiring diagrams may indicate the G65 signal connection as being "Coolant fan control module connection" .
- ECM terminal number assignments correspond with those on test box VAG 1598A .

- Connect green clip from VAG 1767 to the corresponding numbered position on test box VAG 1598A connected to G65 pin - 2 - using appropriate VAG 1594 adapter cable - 7 - . Example: 61

Checking
- Switch ignition on.
- Press button - arrow - for Duty Cycle measurement (modulation ratio) on ignition tester VAG 1767 (or select same function on equivalent device).

Evaluating results






Note:
- If a malfunction cannot be located, check DTC memory of Engine Control Module (ECM) and the Transmission Control Module (TCM) using VAG 1551/1552/1552 . When doing so, note that DTCs related to sensor G65 functions may be called-out as "A/C pressure switch -F129-" .