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Why Audi G28 Isn’t A Topic That People Are Interested In.
How to Replace an Audi G28 Engine Speed Sensor 
 
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) and then to the tachometer in the instrument cluster. 
 
1. Engine Speed Sensor 
 
The grey wire is situated on the outside of the transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster. 
 
The sensor is used to link 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 activate spark and injectors according to the situation. 
 
If audi car keys G28 Car Keys fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper chain of timing. However the code will not appear on its own without additional information from other sensors (G4 and G40). 
 
It is a little tricky to test as there are several pins on the connector and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. When the sensor is operational, it should be reading about 1000 ohms. If you’re having issues with this component, look for signs of oil or coolant in the connector bay. 
 
 
2. Injectors 
 
Yesterday, when accelerating from highway paytoll at full speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, three were drenched with gazoline the fourth one was dry. When i crank the engine without sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th one stays shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I’m assuming the issue is elsewhere. 
 
I also tried to reset PID without success. The car can start if the G28 is disconnected and runs fine when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine. 
 
I’m not sure what to do, i think i’ve pretty much eliminated everything else. However, i’m afraid that I might have missed something. If anyone has any suggestions, please let me know! 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 works on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. Test them out – put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector’s end). They should be infinite Ohms. 
 
4. ECU 
 
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown. 
 
Some of the signs of a failing G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or misfiring when in gear. If you experience any of these problems, it is most likely that your sensor is deteriorating and needs replacing. The good news is they are quite affordable and readily available particularly if you’re looking at the Bosch model, which is what we have. Alternately, the GM version of this component is also a great option. 
 
5. Tachometer 
 
A failing engine speed sensor could be the reason behind many issues with your car. It is a crucial part of your Audi’s transmission, since it relays information to the ECU about how fast or slow the car’s crankshaft is turning. When this sensor fails, it can disrupt the performance of the transmission and the other car’s components. 
 
The G5 engine speed sensor is located on the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU then processes this signal to regulate fuel, timig and boost and then transmitting it to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. You can also check continuity between pin 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. There should be the resistance to be around 1000 ohms between these points. This part is common 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 You may also find them in wrecking yards.