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How to Replace an replacement audi key G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission just above the flywheel ring gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends a signal to the G5 tachometer inside the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the location of the camshaft in order to activate the spark and injectors.

If this sensor fails, the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. However, the code won't appear on its own without additional information from other sensors (G4 and G40).

It is a little tricky to test because there are several pins on the connector and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading about 1000 ohms. If you are having problems with this sensor, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant decrease in power. It was as if the engine had run 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. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the 3 with gazoline jump out. The 4th one remains shut. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero ohm. Therefore, service i think the issue is in another place.

I also tried to reset the PID but with no luck. The car will start if the G28 is not plugged in and is running fine when it is plugged in however it has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also i noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, but i feel i have pretty much eliminated everything else. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sender is the same as the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or from a parts store. Test them out by putting your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They should 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 in order to make decisions regarding timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor service G28 to accomplish this. If you have a problem with either of these, the diagnostic scanner will show codes that could cause an engine shut down.

Some of the signs of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you are in gear. It is possible that the sensor is failing and needs to be replaced if you notice any of these signs. The good news is that they are very cheap and easy to find, especially if you're looking at an Bosch model, which is what we have. Alternately, the GM version of this component is also a good choice.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of problems in your vehicle. It's a vital component of the audi tt replacement key's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is rotating. When this sensor fails, it will cause problems for the transmission and the other car's components.

The G5 engine sensor is located at the edge of the transmission, over the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig, and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should observe around 1000 ohms of resistance between those points. This is a typical part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.