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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, above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer within the instrument cluster. 1. Engine Speed Sensor The grey wire is situated on the outside of the transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends signals to the G5 tachometer inside the instrument cluster. The sensor is used to link with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors accordingly. If this sensor fails when it fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in line 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 appear on its own, without additional information from other sensors (G4 and G40). It can be a bit difficult to test as there are several pins on the connector, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is operational, it should read approximately 1000 ohms. If you're having issues with this sensor, look for signs of oil or coolant in the connector bay. 2. Injectors Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a massive decrease in power. It was like the engine had run out of gas. Or, my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I put tissue over each hole in the injector and when i start the engine without sparks, the ones with gazoline jump out. The 4th one remains closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. I think the issue is elsewhere. I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. audi a1 key replacement (G62) even when it is unplugged, shows a temperature of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine. I'm not certain what to do, as i feel i have pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has any ideas please share them! 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. It is easy to find an extra in a wrecking shop or a parts store. It is easy to test them – simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed of the crankshaft to determine timing of fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner which could cause engine shut down. A damaged G28 sensor could result in an inaccurate speed counter for the gearbox and a gearbox which shifts faster than normal, and/or a misfire while in the gear. It is likely that your sensor is failing and requires to be replaced if you experience any of these symptoms. The good thing is that they are quite affordable and easily accessible, especially when you're looking at the Bosch sensor, like ours. Alternatively, the GM version of this part is also a great option. 5. Tachometer A faulty engine speed sensor could be a cause for a slew of issues in your car. It's an essential component of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is spinning. If the sensor fails, it can cause problems for the transmission and the other car's components. The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost, and also transmitting it to the G5 Tachometer located in the instrument cluster. You can check 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 [79]) and between pin T6a/1 as well as pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This is a typical part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.