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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 near the transmission's edge over the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster. 1. Engine Speed Sensor The grey wire is situated on the edge of transmission, directly above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. audi a3 replacement key utilizes this information to control fuel and boost. It also sends signals to the G5 Tachometer located in the instrument cluster. The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors in the right way. If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40). Testing can be a bit difficult because there are two connector pins, and they serve different purposes however the best way to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is operating at its maximum. Look for signs of coolant, or oil in the connector bay if you are experiencing issues with this component. 2. Injectors Yesterday, while accelerating from the highway paytoll at full speed I noticed a massive reduction in power. It was like the engine was running out of gas. Or, my injectors weren't firing. This morning i pull out the spark plugs, 3 were soaked with gazoline and the fourth one was dry. I placed a tissue over each injector hole, and when I turn the engine on without sparks, the 3 that have gazoline pop right out. The 4th one stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got 0ohm. I'm assuming the issue is elsewhere. I also tried to reset PID without success. The car can start if the G28 is unplugged and it runs perfectly when it is plugged in however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero. I'm not sure what to do. I believe that I've all other possibilities out. But i am afraid I may have missed something. If anyone has suggestions, 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 sender is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. It is simple 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 of our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes badly, you will see codes on the diagnostic scanner which could cause engine shut down. Some of the symptoms of a failed G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or misfiring when you are in gear. If you experience any of these issues it is most likely that your sensor is deteriorating and requires replacement. They're inexpensive and easy to locate especially when they're a Bosch unit like ours. Alternatively, the GM version of this component is also a great option. 5. Tachometer A malfunctioning engine speed sensor could be the cause of a slew of issues in your vehicle. It's a vital component of your Audi's transmission, because it communicates to the ECU about how the car's crankshaft is turning. If the sensor fails, it can disrupt the performance of the transmission, as well as the rest of the car's components. The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU is then able to process the signal to control the flow of fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect a resistance of approximately 1000 ohms between these points. This is the same across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU You may also find them in wrecking yards.