20 Myths About Audi G28: Busted

How to Replace an audi a3 spare key G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission, above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using the grey wire. The ECU uses this information to regulate fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two pins for the connector and they perform different functions however the best way to test it is by measuring resistance between the sensor and the ECU. It should read around 1000 ohms if the sensor is in full operation. If you're having issues with this sensor, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll i had a big cut in power like the engine is running out of gas or injectors are not firing anymore. I took out the spark plugs this morning, three were drenched in gasoline and the fourth was unclean. I put tissue over each hole in the injector and when I start the engine with no sparks, the ones with gazoline jump out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. I think the issue is somewhere else.

I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I don't know what to do. I think I've ruled everything else out. But i am afraid i might have missed something. If anyone has any suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. It is easy to test them - simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, for example. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.

The signs of a failing G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when you are in gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these symptoms. They are cheap and easy-to-find, especially if they're a Bosch sensor like ours. If you prefer, GM's version of this part would be an option.

5. Tachometer

A failing engine speed sensor could be a cause for a slew of issues with your car. It's an essential component of your audi key fobs's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. When this sensor fails, it can affect the performance of the transmission and the other car's components.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends an electrical signal through a gray wire to the ECU pin T55/49. The ECU then processes this signal to control fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between these two points. This part is common across the replacement audi car key tt replacement key for audi a3 fob (meshbookmarks.com) 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU You may also find good ones in wrecking yards.