20 Myths About Audi G28: Dispelled
How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is located at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through the grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu must know when the crankshaft reached TDC and also the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper timing chain. However, the error code won't appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different pins for the connector and they perform different functions but the best way to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is in full operation. If you are having problems with this sensor, look for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs, 3 were soaked with gazoline and the fourth was dry. I put tissue over each injector hole, and when i start the engine without sparks, the ones 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 0ohm. I think the issue is elsewhere.
I also tried to reset PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. Also audi replacement keys noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.
I don't know what to do. I feel like i've pretty much eliminated everything else. I'm concerned that i may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find a spare in a wrecking shop or a parts store. It is simple to test them to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft to determine timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.
Some of the signs of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you're in gear. It is likely that the sensor is failing and requires to be replaced if you encounter any of these signs. The good news is they are very cheap and easy to find, especially if you're looking at an Bosch model, which is what ours are. You can also choose the GM version of this component is also a good choice.
5. Tachometer
A faulty engine speed sensor could be the cause of numerous problems in your car. It is a crucial part of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is turning. If the sensor fails, it could affect the performance of the transmission and the other 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 through an uncolored wire. The ECU then processes this signal to control fuel, timig, and boost and then transmitting it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can 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 and pin T26a/12. You should observe approximately 1000 ohms resistance between these two points. This part is common across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du, so you might find some good ones in wrecking yards.