Ur quattro flywheel sensors

lefthooker · 12-09-21, 02:45 PM

One plugs into the ECU loom, the other into the engine loom. Not sure which way around they should be as the connections appear to be identical, can anyone help?

Car is a 1981 WR.

Colin Aitchison · 12-09-21, 08:40 PM

They both got back to the ECU, G4 - Ignition timing sensor, fits into the left rear of the engine block and looks for the timing pin on the rear of the flywheel , G28 - Engine speed sensor, fits into the top front edge of the gear box and counts the flywheel teeth, never fitted them round the wrong way, so can not confirm if that causes problems.

lefthooker · 13-09-21, 04:06 PM

Quote:

Originally Posted by Colin Aitchison

They both got back to the ECU, G4 - Ignition timing sensor, fits into the left rear of the engine block and looks for the timing pin on the rear of the flywheel , G28 - Engine speed sensor, fits into the top front edge of the gear box and counts the flywheel teeth, never fitted them round the wrong way, so can not confirm if that causes problems.

Thanks for that. Found that they do indeed both go back to the ECU

Still need to find out which is which, probably going to end up a case of trial and error.

Colin Aitchison · 13-09-21, 04:22 PM

Just had a look at the wiring diagram, G4 and G28 connect to the ECU pins as follows, G4 connects to pin 12, 13 and 25, 25 is the earth shield, 12 and 13 are the siginal wires, G28 connects to pin 11, 24 and 23, 23 is the earth shield, 11 and 24 are the siginal wires. There are two or three ways to test this with an AVO. but all involve removing the cable connector from the back of the ECU for testing.

lefthooker · 13-09-21, 04:33 PM

Quote:

Originally Posted by Colin Aitchison

Just had a look at the wiring diagram, G4 and G28 connect to the ECU pins as follows, G4 connects to pin 12, 13 and 25, 25 is the earth shield, 12 and 13 are the siginal wires, G28 connects to pin 11, 24 and 23, 23 is the earth shield, 11 and 24 are the siginal wires. There are two or three ways to test this with an AVO. but all involve removing the cable connector from the back of the ECU for testing.

That's excellent info. Thanks very much for your help.

mikes2 · 13-09-21, 05:01 PM

They're normally colour coded.

G4 is black

G28 will be grey

lefthooker · 14-09-21, 12:31 PM

Quote:

Originally Posted by mikes2

They're normally colour coded.

G4 is black

G28 will be grey

Thanks for that

13-09-21, 05:01 PM	#6
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	They're normally colour coded. G4 is black G28 will be grey __________________ 1991 90 quattro 20v sport 1991 90 quattro

12-09-21, 08:40 PM	#2
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,308	They both got back to the ECU, G4 - Ignition timing sensor, fits into the left rear of the engine block and looks for the timing pin on the rear of the flywheel , G28 - Engine speed sensor, fits into the top front edge of the gear box and counts the flywheel teeth, never fitted them round the wrong way, so can not confirm if that causes problems.

13-09-21, 04:22 PM	#4
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,308	Just had a look at the wiring diagram, G4 and G28 connect to the ECU pins as follows, G4 connects to pin 12, 13 and 25, 25 is the earth shield, 12 and 13 are the siginal wires, G28 connects to pin 11, 24 and 23, 23 is the earth shield, 11 and 24 are the siginal wires. There are two or three ways to test this with an AVO. but all involve removing the cable connector from the back of the ECU for testing.