How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is located at the edge of transmission just above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU uses this information to control fuel and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
similar web page is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can start spark and injectors accordingly.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment 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. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging because there are two connector pins, and they serve different purposes but the best way to test it is to measure resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading around 1000 ohms. If you're having issues with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday accelerating full speed from highway paytoll, i experienced massive power loss like the engine is running out of gas or injectors are not firing any more. Today, i pulled out the spark plugs, three were soaked with gazoline and the 4th one was dry. I placed a tissue over each injector hole and when i start the engine without sparks, the three that have gazoline pop right out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I'm assuming that the issue is elsewhere.
I also tried to reset the PID without success. The car can start if the G28 is unplugged and is running fine when it is connected however it has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil pressure gauge in the cockpit shows 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 ruled everything else out. But i'm worried that I may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or parts store. It is easy 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 should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft to determine timing of fuel injectors, etc. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that can cause the engine to shut down.
A failing G28 sensor could cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or a misfire while in gear. If you experience any of these problems, it is likely your sensor is going bad and should be replaced. They're cheap and easy to find especially if they're a Bosch sensor like ours. Alternately, GM's version this component is an option.
5. Tachometer
A malfunctioning engine sensor can cause a variety of issues in your vehicle. It is an important part of the transmission of your Audi, as it transmits information to the ECU regarding how fast or slow the car's engine is turning. If the sensor fails, it will cause problems for the transmission and the other car's components.
The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins 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 observe approximately 1000 ohms of resistance between those points. This is the same across the Audi 80-100-200-RS2 model, ranging from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 Du You may also find them in wrecking yards.