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. This sensor is located at the top of the transmission just above the flywheel ring gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC and also where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit tricky 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 fully operational, it should read approximately 1000 ohms. Examine for evidence of coolant or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. When I crank the engine with no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID but without success. The car is able to start if the G28 is unplugged and runs fine when it is plugged in however it has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.
I don't know what to do. audi car keys replacement believe that I've all other possibilities out. I'm worried that i might have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter functions similarly 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 a parts store. It is simple to test them to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know the speed and position of the crankshaft to make decisions regarding fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could cause an engine shut down.
A damaged G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or an unfire when in gear. If you experience any of these problems, it is likely that your sensor is deteriorating and should be replaced. The good news is they are very affordable and easily accessible particularly if you're looking at a Bosch unit which is what ours are. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine sensor could cause a variety of issues in your vehicle. It is a crucial part of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is spinning. When this sensor fails, it can cause problems for the transmission as well as the other car's components.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends an electrical signal through a gray wire to the ECU pin T55/49. The ECU uses this signal to control the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the continuity from the sensor to the tachometer. You can also 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 and pin T26a/12. You should see approximately 1000 ohms of resistance between those two pins. This is a common part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.