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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer located on the instrument cluster. 1. Engine Speed Sensor Located on the edge of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical 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 an indication to the G5 Tachometer located in the instrument cluster. The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and 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 code. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40). Testing can be a bit difficult as there are two different connector pins, and they perform different functions but the most effective method to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should read approximately 1000 ohms. Look for signs of coolant or oil in the connector bay if you have issues with this part. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a significant decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning and found that 3 were soaked with 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 three with gazoline jump out. The 4th one remains closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. I'm assuming the issue is in another place. I also tried to reset the PID without success. The car will start if the G28 is not plugged in and runs fine when it is connected, but still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine. I'm not sure what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that I might have missed something. If anyone has any ideas please chime in! TIA! 3. Fuel Pump The fuel pump on the g28 is activated by a signal sent by the RPM sensor. lost audi keys -style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare 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 end). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know both the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. To accomplish this, it utilizes 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 show the codes that could trigger an engine shutdown. A failing G28 sensor could result in an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or a misfire while in gear. It is probable that your sensor is failing and requires to be replaced if you experience any of these signs. The good thing is that they are quite affordable and easily accessible, especially if you're looking at a Bosch model, which is what we have. You can also choose the GM version of this unit is also a good choice. 5. Tachometer A damaged engine sensor could cause a variety of issues in your vehicle. It is a crucial part of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. If the sensor fails, it can cause problems for the transmission, as well as the rest of the car's components. The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU uses this signal to control the amount of fuel and boost, and also timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms in these areas. This is a standard component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.