How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is situated at the edge of transmission just above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. 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 be aware of when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails when it fails, 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 the possibility of a chain stretch or jumped chain link in the upper timing chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging because there are two connector pins and they serve different purposes but the most effective method to test it is to measure resistance between the sensor and the ECU. It should read about 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 part.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were drenched in gasoline and the fourth was dry. When I start the engine, there are no sparks, i place a tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th one stays closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. So i assume the problem 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 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 bars while the actual pressure is zero.

I don't know what to do. I feel like i've pretty much all other possibilities out. But i'm worried that I may have missed something. If anyone has suggestions, please let near me know! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter functions similarly 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 parts store. Testing them is easy - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's 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 must know the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either one of these, the diagnostic scanner will display the codes that could trigger an engine shutdown.

A damaged G28 sensor could result in an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, and/or a misfire in the gear. It is possible that the sensor is failing and requires to be replaced if you notice any of these symptoms. The good news is that they are quite affordable and easily accessible particularly if you're looking at an Bosch unit which is what ours are. Alternately, GM's version this part is an excellent choice.

5. Tachometer

A malfunctioning engine speed sensor could be a cause for numerous issues with your car. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.

The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU then uses and processes this signal to control fuel, timig and Near Me boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should observe approximately 1000 ohms resistance between these two points. This is a common part across the audi keys 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.