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How to Replace an Audi G28 Engine Speed Sensor Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49), then to the tachometer in the instrument cluster. 1. Engine Speed Sensor Located on the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer within the instrument cluster. The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors accordingly. If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40). Testing can be a bit difficult since there are two connector pins, and they serve different purposes but the most effective method of testing it is by measuring resistance between the sensor and the ECU. When new audi key is fully operational, it should be reading 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 maximum speed, i noticed a huge reduction in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put tissue over each hole in the injector and when i start the engine with no sparks, the three with gazoline jump out. The 4th one remains closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. I assume that the problem is elsewhere. I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even when it is unplugged, shows an ice temperature of -49c. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine. I'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm afraid i may have missed something. Let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or parts store. It is simple to test them – just put your DMM into resistance mode and test 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 be aware of the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes bad you will get codes on the diagnostic scanner that can lead to engine shutdown. A failing G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, and/or a misfire while in gear. If you are experiencing any of these issues it is likely your sensor is failing and requires replacement. The good news is they are very affordable and readily available particularly if you're looking at the Bosch sensor, which is what we have. Alternately, GM's version this component is an option. 5. Tachometer A malfunctioning engine speed sensor could be the cause of a slew of issues in your vehicle. It's a crucial component of the transmission in your Audi because it relays information to the ECU on how fast or slowly the engine of the car is spinning. This sensor could cause the transmission to malfunction and other components in the car to be affected. The G5 engine speed sensor is located at the outside of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost as well as sends it on to the G5 tachometer in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see approximately 1000 ohms resistance between those points. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du So, you may find them in wrecking yards.