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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. The sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer on the instrument cluster. 1. Engine Speed Sensor The sensor is located at the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using the grey wire. The ECU uses this information to control boost and fuel. It also sends an alert to the G5 Tachometer within the instrument cluster. The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation. If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jump in the chain link of the upper chain of timing. However, the error 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 have different functions but the best method to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is at full operation. If you are having problems with this sensor, look for evidence 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. I took out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was unclean. When i crank the engine without sparks i put tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th one stays closed. I tested the ground connection of ECU pins 14,30 and 48/55. www.g28carkeys.co.uk found zero ohm. I assume that the problem is somewhere else. I also tried to reset the PID with no success. The car is able to start when the G28 is not plugged in and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0. I don't know what to do. I feel like i've pretty much eliminated everything else. However, i'm afraid that I might have missed something. Let me know If 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 functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. Test them out by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They should be infinite Ohms. 4. ECU Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that has to be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down. A failing G28 sensor can cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, and/or an unfire when in the gear. It is likely that your sensor is failing and needs to be replaced if you encounter any of these signs. They're cheap and easy to find especially if they're an Bosch sensor like ours. Alternatively, the GM version of this component is also a good choice. 5. Tachometer A malfunctioning engine speed sensor could be the reason behind a slew of problems in your car. It is a crucial part of the Audi's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor could cause the transmission to malfunction and other components in the car to be affected. The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU uses 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 determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should see the resistance to be around 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU So, you may find them in wrecking yards.