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 situated on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU through the grey wire T55/49 and then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is located at the edges 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 boost, fuel, and timig. It also sends an indicator to the G5 Tachometer in instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also where the camshaft lies so that it can activate the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate an issue with the chain or a jumped chain link in the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging since there are two connector pins, and they perform different functions but the most effective method to test it is to measure the resistance between the sensor and the ECU. https://canvas.instructure.com/eportfolios/3193191/Home/Responsible_For_The_Audi_A4_Key_Replacement_Budget_12_Tips_On_How_To_Spend_Your_Money should read approximately 1000 ohms when it is at full operation. If you're experiencing issues with this sensor, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a significant drop in power. It was like the engine was running out of gas. Or my injectors weren't firing. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. When i crank the engine without sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th one stays closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 i get 0ohm. I'm assuming that the issue is somewhere else.

I also tried to reset the PID but with no luck. The car can start when the G28 is not plugged in and it runs perfectly when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not sure what to do, but i believe that i've ruled out everything else. I'm afraid i may have missed something. Please let me know if you have any ideas! TIA!



3. Fuel Pump

The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or from a parts store. Test them out - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft in order to make decisions about timing of the fuel injector, for example. 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 wrong, you will receive codes on the diagnostic scanner which can cause the engine to shut down.

A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, or a misfire while in the gear. It is possible that your sensor is failing and needs to be replaced if you encounter any of these signs. They are cheap and easy-to-find especially in the case of an Bosch model like ours. Alternatively, GM's version of this part is an excellent choice.

5. Tachometer

A failing engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission in your Audi since it sends information to the ECU regarding how fast or slowly the engine of the car is turning. This sensor could cause the transmission to malfunction and other components of the car to be affected.

The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to regulate fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer inside the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms of resistance between those points. This is a standard 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. Good ones could be available in wrecking yards.