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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 just above the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer in 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 a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer in instrument cluster. The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC, and the position of the camshaft, to trigger the spark and injectors. If this sensor fails, the ECU will show the P00160 error, 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 chain of timing. However, the error code won't appear on its own without additional information from other sensors (G4 and G40). It is a little tricky to test since there are different pins on the connector and each one has different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is in full operation. Look for signs of coolant or oil in the connector bay if there are problems with this part. 2. Injectors Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced a big cut in power as if the engine was running out of gas or injectors are not firing anymore. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. When I crank the engine without sparks, i place a tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I think the issue is somewhere else. I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 when i rev the engine. official website don't know what to do. I think I've eliminated everything else. But i am afraid I may have missed something. Please let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump on the g28 is activated by a signal sent from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms. 4. ECU The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed of the crankshaft to make decisions regarding timing of the fuel injector, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could cause the engine shutting down. A failing G28 sensor can cause an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, and/or an unfire when in gear. It is possible that the sensor is failing and needs to be replaced if you notice any of these signs. The good news is that they are very affordable and easy to find, especially if you're looking at a Bosch unit like ours. You can also choose the GM version of this unit is also a good choice. 5. Tachometer A failing engine speed sensor could be the cause of a slew of issues with your vehicle. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is rotating. If the sensor fails, it can disrupt the performance of the transmission and the other car's components. The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to control fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. It should show around 1000 ohms of resistance between these two points. This is a typical component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.