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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 on the outside of the transmission, above the flywheel gear. It sends a signal to the ECU via the grey wire (T55/49), then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using a grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors according to the situation.
If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy chain link in the upper chain of timing. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit tricky as there are two different pins for the connector and they serve different purposes however the best method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is operating at its maximum. Check for signs of coolant, or oil in the connector bay if there are problems with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge decrease in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning, 3 were soaked with gasoline and the fourth was unclean. When I crank the engine, there are no sparks i put tissue on the top of each of the injector holes and the 3 that were drenched in gazoline pop out, but the 4th stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. new audi car key got 0ohm. I assume that the problem is somewhere else.
I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it is running fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.
I'm not sure what to do, i believe that i've ruled out everything else. But i am afraid I may have missed something. Let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or parts store. It is simple to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY) engines must know the speed and position of the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.
A failing G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire while in the gear. It is probable that the sensor is failing and requires to be replaced if you experience any of these symptoms. The good thing is that they are quite affordable and readily available, especially when you're looking at an Bosch model, like ours. Alternatively, the GM version of this part is also a good option.
5. Tachometer
A failing engine speed sensor could be the cause of many issues with your vehicle. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is spinning. If this sensor fails, it will cause problems for the transmission and the rest of the car's components.
The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining 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 see approximately 1000 ohms resistance between those points. This is a common part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.