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 near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49) and then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends an indication to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors in the right way.
If this sensor fails, the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing can be a bit difficult because there are two connector pins and they perform different functions but the most effective method to test it is to measure resistance between the sensor and the ECU. When the sensor is fully functional, it should read about 1000 ohms. Check for signs of coolant, or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll i had a big cut in power like the engine is out of gas or the injectors aren't firing anymore. I pulled out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was unclean. I put tissue over each hole in the injector and when I start the engine with no sparks, the ones with gazoline jump right out. The fourth one remains shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. Also, i noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do. I feel like i've pretty much ruled everything else out. But advanced key audi am afraid i might have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or parts store. It is simple to test them to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines needs to know both the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. In order to do this it makes use of 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 could cause engine shut down.
A damaged G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, and/or a misfire in gear. It is possible that the sensor is failing and requires to be replaced if you encounter any of these signs. The good news is that they are very affordable and readily available, especially when you're looking at an Bosch unit which is what ours are. You can also choose the GM version of this component is also a good choice.
5. Tachometer
A malfunctioning engine sensor can cause a variety of issues in your car. It's a crucial component of the transmission in your Audi, as it transmits information to the ECU on how fast or slow the engine is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to control the flow of fuel and boost and also timig. It also sends it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Also, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 and pin T26a/12. You should observe around 1000 ohms of resistance between those 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 the 1995 RS2 DU So, you may find them in wrecking yards.