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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 on the outside of the transmission just above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within the instrument cluster. 1. Engine Speed Sensor Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends a signal to the G5 tachometer in the instrument cluster. The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors in the right way. If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in sync 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 of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40). Testing is a bit tricky as there are two different connector pins, and they perform different functions however the best method to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should be reading around 1000 ohms. If you're having issues with this part, check for evidence of coolant or oil in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is running out of gas or injectors are not firing at all. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. When I start the engine without sparks, i place a tissue on the top of each of the injector holes, the 3 drenched with gazoline pop out, but the 4th one stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. Therefore, i think new audi key is somewhere else. I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I don't know what to do. I think I've all other possibilities out. I'm worried that i might have missed something. Please let me know should you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or 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 left on the black connector's end). They should be infinite ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you encounter a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shut down. The signs of a failing G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you're in gear. It is likely that the sensor is failing and requires to be replaced if you notice any of these symptoms. They're inexpensive and easy to locate particularly if they're an Bosch model like ours. Alternately, the GM version of this component is also a great option. 5. Tachometer A failing engine sensor could cause a variety of issues in your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU regarding how fast or slowly the engine is turning. If the sensor fails, it will affect the performance of the transmission and the other car's components. The G5 engine speed sensor is located on the edge 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 ECU utilizes this signal to regulate the flow of fuel and boost and also timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from 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 and pin T26a/12. You should see an average resistance of 1000 ohms in these areas. This is a typical part across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.