How to Replace an audi replacement key fob G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, just above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to control fuel and boost. It also sends an indication to the G5 Tachometer in instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC and also the location 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 be a sign of a chain stretch or a jumped chain link in the upper chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing can be a bit difficult since there are two pins for the connector and they serve different purposes but the best method of testing it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is operating at its maximum. Look for signs of coolant, or oil in the connector bay if you have issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I start the engine without sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I'm assuming the issue is in another place.

I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor audi A1 key fob (G62), even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.

I'm not certain what to do, i believe that i've eliminated everything else. But i am afraid I might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by 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 parts store. It is simple to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and audi A1 key Fob 2 (with the bump at the connector's end facing up). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or a misfire in gear. It is likely that the sensor is failing and requires to be replaced if you notice any of these symptoms. The good news is that they are very affordable and readily available particularly when you're looking at the Bosch model, like ours. Alternately, the GM version of this part is also a good choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues in your car. It's an essential component of your audi spare key's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between these two points. This is a common feature across the audi a1 key fob 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du, so you might find some good ones in wrecking yards.