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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 located on the outside of the transmission over the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends an indication to the G5 Tachometer located in the instrument cluster. The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC, and where the camshaft lies to trigger the spark and injectors. If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain stretching or a jump link on the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40). Testing is a bit tricky since there are two pins for the connector and they have different functions but the most effective method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should read approximately 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay. 2. Injectors Yesterday, when accelerating from highway paytoll at full speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. When I start the engine without sparks i put tissue on the top of each of the injector holes and the 3 drenched with gazoline leap out, however the 4th stay closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. Therefore, i think the issue is in another place. I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero. I don't know what to do. I think I've ruled everything else out. I'm concerned that i may have missed something. Please let me know if you have any ideas! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style sender is the same as the G4 and both function in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or from a parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines must know both the speed and position of the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go badly, you will see codes on the diagnostic scanner that could cause engine shut down. Some of the signs of a failed G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you're in gear. It is probable that the sensor is failing and needs to be replaced if you experience any of these signs. They're inexpensive and easy to locate, especially if they're an Bosch sensor like ours. If you prefer, GM's version of this part would be an excellent choice. 5. Tachometer A failing engine sensor could cause a myriad of issues within your vehicle. It's an essential component of the transmission of your Audi since it sends information to the ECU about how fast or slow the engine is turning. When advanced key audi fails, it will disrupt the performance of the transmission as well as the other car's components. The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate the amount of fuel and boost, and also timig. It also sends it to the G5 Tachometer in instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du, so you might find them in wrecking yards.