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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. G28CarKeys is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor It is located on the outside of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 tachometer in the instrument cluster. The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the location of the camshaft so that it can activate the spark and injectors. If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jump in the chain link of 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 since there are two connector pins and they perform different functions but the best way to test it is to measure resistance between the sensor and the ECU. When the sensor is fully functional, it should read about 1000 ohms. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay. 2. Injectors Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power like the engine is running out of gas or injectors aren't firing anymore. In the morning, i removed the spark plugs, 3 were drenched with gazoline the fourth one was dry. When i crank the engine, there are no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 that were drenched in gazoline leap out, however the 4th stay shut. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. So i assume the problem is elsewhere. I also tried to reset the PID without success. The car can start if the G28 is disconnected and is running fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (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 is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I'm not sure what to do, as i feel i have pretty much eliminated everything else. I'm concerned that i may have missed something. Let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 gets 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. You can easily find the spare in a salvage shop or parts store. It is easy to test them – just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown. The signs of a failing G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal and/or a misfire when in gear. It is possible that your sensor is failing and requires to be replaced if you experience any of these symptoms. The good news is they are very cheap and easy to find, especially when you're looking at the Bosch unit which is what we have. Alternately, the GM version of this unit is also a good choice. 5. Tachometer A failing engine speed sensor could be a cause for many issues with your vehicle. It's an essential component of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is turning. This sensor could 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, just above the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to control fuel and boost, and also timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should observe 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 until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.