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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 at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor is used to connect with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC and also the position of the camshaft, to trigger the spark and injectors.
If this sensor fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain. However, the code won’t be displayed on its own without additional information from other sensors (G4 and G40).
audi keys is a little tricky to test since there are various connector pins, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms when it is in full operation. If you’re experiencing issues with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from 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. I pulled out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was unclean. I placed a tissue over each hole in the injector and when I start the engine without sparks, the ones that have gazoline pop right out. The 4th one stays closed. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID with no success. The car will start if the G28 is disconnected and it runs perfectly when it is connected however it has the intermittent misfire issue at higher RPM. The coolant temperature sensor (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 0.
I’m not sure what to do, but i think i’ve pretty much completely ruled out all other possibilities. However, i’m afraid that I may have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style sensor is the same as the G4 and both function in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector’s edge facing upwards). They must be infinite ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft to determine fuel injector timing, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will display the codes that could trigger an engine shut down.
The signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter the gears are shifting faster than normal and/or a misfire when you’re in gear. It is possible that your sensor is failing and needs to be replaced if you notice any of these signs. They are cheap and easy-to-find, especially if they’re an Bosch unit like ours. Alternately, GM’s version this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It is an important part of the transmission of your Audi, as it transmits information to the ECU on how fast or slow the engine of the car is spinning. If the sensor fails, it could disrupt the performance of the transmission and the rest of the car’s components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Also, 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. It should show approximately 1000 ohms resistance between those two pins. This is a standard component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.