How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located at the edges of the transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to regulate fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC, and 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 indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test because there are different pins on the connector, and they all have different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms when it is at full operation. Look for evidence of coolant or oil in the connector bay if you have issues with this component.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced massive power loss like the engine is out of gas or injectors are not firing anymore. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the 4th was dry. I placed a tissue over each injector hole and when i start the engine with no sparks, the 3 with gazoline jump out. The 4th one remains closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero Ohm. I'm assuming that the issue is somewhere else.

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 connected. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. 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 get more info do, but i feel i have pretty much ruled out everything else. I'm concerned that i may have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a here spare in a wrecking shop or a parts store. Testing them is easy to do - just put here your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the position and read more speed the crankshaft to make decisions regarding timing of the fuel injector, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

A malfunctioning G28 sensor could result in an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in gear. It is likely that the sensor is failing and needs to be replaced if you notice any of these signs. They're inexpensive and easy to locate especially if they're a Bosch model like ours. Alternatively, the GM version of this component is also a good option.

5. Tachometer

A failing engine speed sensor could be the reason behind numerous issues with your car. It's an essential component of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is turning. If this sensor fails, it can disrupt the performance of the transmission and the rest of the car's components.

The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The more info ECU then uses and processes this signal to control fuel, timig, and boost and then sends it on to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin 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. There should be a resistance of approximately 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU You may also find some good ones in wrecking yards.