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How to Replace an audi key fob G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located on the outside of the transmission just above the flywheel gear. It transmits a signal to the ECU through 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 G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using a grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an alert to the G5 Tachometer in instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors in the right way.

If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumped chain link in the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging because there are two connector pins 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 when the sensor is in full operation. Examine for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge drop in power. It was like the engine was running out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, 3 were drenched in gazoline, the 4th one was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the ones that have gazoline pop right out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. So i assume the problem is in another place.

I also tried to reset PID but without success. The car is able to start when the G28 is disconnected and runs fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.

I'm not sure what to do, but i believe that i've completely ruled out all other possibilities. But i am afraid I may have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is simple to test them - just put your DMM into resistance mode and test the distance between pins 1 and 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 be aware of the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these audi keyless go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, or an unfire when in gear. If you have any of these issues it is likely your sensor is failing and needs replacing. They are cheap and easy-to-find, especially in the case of an Bosch unit like ours. Alternately, GM's version this part would be an option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your car. It is an important part of the transmission of your audi replacement key fob, as it transmits information to the ECU about how fast or slow the engine is turning. This sensor can cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits signals via a gray wire to the ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer 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 on pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see a resistance of approximately 1000 ohms between these points. This is a common feature across the audi tt key Programming 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 Du So, you may find some good ones in wrecking yards.