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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 located on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor It is located on the outside of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 via a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer in instrument cluster. The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors in the right way. If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the code won't appear on its own without additional information from other sensors (G4 and G40). Testing is a bit challenging because there are two pins for the connector and they serve different purposes but the best way to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should read around 1000 ohms. If you're experiencing issues with this sensor, look for evidence of coolant or oil in the connector bay. 2. Injectors Yesterday, when i was accelerating to the fullest speed from highway paytoll i had massive power loss like the engine is out of gas or injectors are not firing anymore. This morning i pull out the spark plugs, three were drenched in gazoline, the fourth one was dry. When I start the engine without sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline leap out, however the 4th stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. I think the issue is elsewhere. I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged and it runs perfectly when it is connected, but still has the intermittent misfire issue at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine. I'm not certain what to do, i believe that i've ruled out everything else. I'm afraid i may have missed something. If what to do if you lose your audi key has suggestions, please let me know! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is similar to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. Test them out – put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black end of the connector). They should be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines requires to be aware of the speed and position of the crankshaft to determine timing of the fuel injector, etc. To do this, it uses 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 which could cause engine shut down. A damaged G28 sensor could cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, or a misfire while in the gear. If you are experiencing any of these issues, it is likely that your sensor is deteriorating and should be replaced. The good news is they are very affordable and readily available, especially if you're looking at a Bosch sensor, which is what we have. Alternately, GM's version this component is a good option. 5. Tachometer A failing engine speed sensor could be the reason behind a slew of problems in your car. It's an essential component of the transmission of your Audi, as it transmits information to the ECU on how fast or slow the car's engine is spinning. If the sensor fails, it will affect the performance of the transmission, as well as the rest of the car's components. 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 processes this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins 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. You should see approximately 1000 ohms of resistance between these two points. 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.