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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. This sensor is situated on the outside of the transmission just above the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer inside the instrument cluster. The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way. If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain. However, the error code won't appear on its own without additional information from other sensors (G4 and G40). Testing is a bit challenging as there are two different pins for the connector and they serve different purposes however the best method of testing it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. Examine for signs of coolant, or oil in the connector bay if there are issues with this part. 2. Injectors Yesterday accelerating full speed from highway paytoll i had massive power loss like the engine is running out of gas or the injectors are not firing any more. In the morning, i removed the spark plugs, three were drenched in gazoline, the fourth was dry. I put tissue over each injector hole, and when I start the engine with no sparks, the 3 with gazoline jump right out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. So i assume audi spare key is elsewhere. I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62), even when it is unplugged, 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 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. Let me know should you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is similar 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 a parts store. It is easy to test them – just put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite ohms. 4. ECU Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that must know the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, for example. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will display codes that could lead to the engine shutting down. A damaged G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, and/or a misfire while in the gear. If you are experiencing any of these problems, it is likely your sensor is deteriorating and should be replaced. The good news is that they are very affordable and easy to find, especially in the case of the Bosch unit like ours. Alternatively, GM's version of this component is an option. 5. Tachometer A failing engine speed sensor could be a cause for a slew of issues in your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU on how fast or slowly the car's engine is spinning. This sensor could cause the transmission to malfunction and other components of the car to be affected. The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU is then able to process the signal to control fuel, timig and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. You can also 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 and pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This is a typical part that is found 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.