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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 located on the edge of the transmission above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster. 1. Engine Speed Sensor The sensor is located at the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using a grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 Tachometer located in the instrument cluster. The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware of when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors. If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on 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 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 when the sensor is in full operation. Look for evidence of coolant or oil in the connector bay if there are issues with this part. 2. Injectors Yesterday, when accelerating from highway paytoll at full speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth was dry. I placed a tissue over each injector hole, and when i start the engine with no sparks, the 3 with gazoline jump out. The 4th one remains shut. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location. I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. Also, i noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine. I'm not certain what to do, but i feel i have pretty much ruled out everything else. I'm concerned that i may have missed something. Please let me know If you have any suggestions! TIA! 3. Fuel Pump The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style sender is identical to the G4 and they both work in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local 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 at the connector's end facing upwards). They should be infinite Ohms. 4. ECU The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed the crankshaft to make decisions regarding timing of fuel injectors, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor ( G28 ). If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown. A damaged G28 sensor could result in an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or an unfire when in the gear. If you experience any of these issues it is likely that your sensor is going bad and should be replaced. The good thing is that they are very affordable and easy to find, especially in the case of a Bosch unit which is what we have. Alternately, GM's version this part is a good option. 5. Tachometer A damaged engine sensor could cause a number of problems in your car. It's an essential component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is spinning. This sensor can cause the transmission to malfunction and other components in the car to be affected. The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test the sensor for any failure by checking the 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 [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 DU You may also find them in wrecking yards.