How to Replace an Audi G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located near the transmission's edge 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 grey wire is located at the edges of the transmission, directly above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors in the right way.

If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't show without the additional information provided by other sensors (G4 or G40).

It can be a bit difficult to test because there are several connector pins, and they all have different functions. audi keys replacement for doing this is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when it is in full operation. Check for evidence of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll i had a big cut in power as if the engine was running out of gas or the injectors aren't firing anymore. This morning i pull out the spark plugs, 3 were drenched in gazoline, the 4th one was dry. When I crank the engine with no sparks i put tissue on the top of each of the injector holes and 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 got 0ohm. Therefore, i think the issue is in another place.

I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not sure what to do. I think I've ruled everything else out. I'm afraid i may have missed something. Please let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. Test them out to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.


4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know both the position and speed of the crankshaft to determine timing of the fuel injector, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will show codes that could cause an engine shut down.

A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. It is likely that the sensor is failing and requires to be replaced if you notice any of these signs. The good news is they are very cheap and readily available, especially if you're looking at an Bosch sensor, like ours. Alternatively, GM's version of this part is a good option.

5. Tachometer

A faulty engine speed sensor could be the cause of many issues in your car. It is a crucial part of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is rotating. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49 via a grey wire. The ECU utilizes this signal to control the flow of fuel and boost and also timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity 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 see around 1000 ohms of resistance between those points. This is a common part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.