How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission, above the flywheel ring gear. It transmits a signal the ECU via an uncolored wire (T55/49) and then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in alignment with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different connector pins, and they have different functions but the best way to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading about 1000 ohms. Check for signs of coolant, or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll i had an abrupt drop in power like the engine is running out of gas or injectors aren't firing at all. This morning i pull out the spark plugs, three were drenched in gazoline, the fourth was dry. When I start the engine with no sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline jump out but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got 0ohm. So i assume the problem is in another place.
I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not sure what to do, but i believe that i've ruled out everything else. However, i'm afraid that i might have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or a parts store. Testing audi a1 key is easy - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's end). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, for example. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.
A malfunctioning G28 sensor can cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, and/or a misfire while in gear. It is likely that your sensor is failing and requires to be replaced if you notice any of these symptoms. They're cheap and easy to find especially if they're an 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 numerous issues with your vehicle. It's a vital component of your Audi's transmission, as it sends information to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate the flow of fuel and boost and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these points. This is a standard part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.