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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is situated at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer in the instrument cluster. 1. Engine Speed Sensor The grey wire is located on the edge of transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster. The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft to trigger the spark and injectors. If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync 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 code won't be displayed on its own without additional information from other sensors (G4 and G40). It's a bit tricky to test since there are different pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is functional, it should read about 1000 ohms. If audi a3 replacement key having issues with this part, check for signs of oil or coolant in the connector bay. 2. Injectors Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss like the engine is out of gas or the injectors aren't firing at all. I pulled out the spark plugs this morning, 3 were drenched in gasoline and the fourth was unclean. When I crank the engine with no sparks i put tissue on the top of each hole in the injector and the 3 drenched with gazoline leap out, however the 4th stay shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I got zero ohm. I'm assuming that the issue is in another location. I also tried to reset the PID but with no luck. The car will start if the G28 is unplugged and is running fine when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0. I'm not sure what to do. I feel like i've pretty much ruled everything else out. I'm worried that i might have missed something. If anyone has suggestions, please share them! TIA! 3. Fuel Pump The fuel pump on the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. Test them out – put 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 side). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY) engines needs to know the position and speed of the crankshaft to make decisions regarding timing of fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger the engine shutting down. A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, or a misfire while in gear. If you have any of these issues it is likely your sensor is failing and requires replacement. They're inexpensive and easy to locate particularly when they're a Bosch unit like ours. Alternately, GM's version this part is an excellent choice. 5. Tachometer A faulty engine speed sensor could be the reason behind numerous problems in your car. It's an essential component of the transmission in your Audi because it relays information to the ECU regarding how fast or slow the engine of the car is turning. When this sensor fails, it can affect the performance of the transmission and the rest of the car's components. The G5 engine speed sensor is situated on the edge of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU then uses and processes this signal to regulate fuel, timig, and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can test 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 on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms of resistance between those points. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU, so you might find them in wrecking yards.