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 situated near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors accordingly.
If this sensor fails, the ECU will display a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump link on the upper timing chain. However, the code won't appear on its own without additional information from other sensors (G4 and G40).
Testing can be a bit difficult as there are two different connector pins and they have different functions however the best method to test it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should be reading around 1000 ohms. Look 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 as if the engine was running out of gas or injectors are not firing any more. In the morning, i removed the spark plugs. Three were drenched in gazoline, the 4th one was dry. I put a piece of tissue over each injector hole, and when i start the engine with no sparks, the 3 that have gazoline pop right out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. i get 0ohm. So i assume the problem is in another place.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, i feel i have pretty much completely ruled out all other possibilities. But i'm worried that I may have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sender is the same as the G4 and both function in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is simple to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that has to know the speed and position of the crankshaft to make decisions about fuel injector timing etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will show codes that could lead to an engine shut down.
A damaged G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, and/or a misfire while in the gear. If you are experiencing any of these issues, it is most likely that your sensor is deteriorating and requires replacement. They're cheap and easy to find, especially in the case of a Bosch model like ours. If you prefer, GM's version of this part would be a good option.
5. Tachometer
A malfunctioning engine speed sensor could be the reason behind numerous problems in your car. 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 turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.
The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It sends an electrical signal through an uncolored wire to the ECU pin T55/49. The ECU then processes this signal to control fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be an average resistance of 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 Du So, you may find some good ones in wrecking yards.