How to Replace an audi keyfob G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace audi key fob the G28 engine speed sensor. This sensor is situated on the outside of the transmission over the flywheel gear. It transmits a signal to the ECU via an uncolored 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, above the flywheel ring. The sensor sends an electrical signal through 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 located in the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the position of the camshaft, to trigger the spark and injectors.

If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump link on the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).

Testing is a bit tricky because there are two pins for the connector and they serve different purposes but the best method to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is at full operation. Check for signs of coolant, or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the 4th was dry. I placed a tissue over each injector hole, and when I start the engine with no sparks, the ones that have gazoline pop right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero ohm. I assume that the problem is somewhere else.

I also tried to reset the PID but with no luck. The car is able to start if the G28 is disconnected and runs fine when it is connected but it still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.

I don't know what to do. I feel like i've pretty much eliminated everything else. I'm worried that i might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or a parts store. It is easy to test them - just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's 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 be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger an engine shutdown.

Some of the symptoms of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when you are in gear. If you have any of these issues, it is likely that your sensor is deteriorating and should be replaced. They are cheap and easy-to-find particularly when they're a Bosch model like ours. You can also choose the GM version of this unit is also a good choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues within your vehicle. It is a crucial part of the audi Tt Replacement key's transmission because it communicates to the ECU about how the car's crankshaft is turning. If this sensor fails, it could cause problems for the transmission as well as the other car's components.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then processes the signal to control fuel, timig, and boost as well as sends it on to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. You should detect an average resistance of 1000 ohms between these points. This is a common feature across the audi key 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du So, you may find some good ones in wrecking yards.