How To Outsmart Your Boss Audi G28

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. The 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), then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using an uncolored wire. The ECU uses this information to control boost and fuel. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors according to the situation.

If this sensor fails the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper chain of timing. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

It is a little tricky to test since there are several pins on the connector and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading approximately 1000 ohms. Examine for signs of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced massive power loss like the engine is running out of gas or the injectors are not firing any more. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth was dry. When i crank the engine with no sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th stays shut. 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 elsewhere.

I also tried to reset the PID but without success. The car is able to start when the G28 is disconnected and runs fine when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant sensor (G62), get more info even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not certain what to do, i believe that i've completely ruled out all other possibilities. However, i'm afraid that I may have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter is identical to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. You can easily locate the spare in a salvage shop or a parts store. It is easy to test them - simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to 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 achieve this. If you encounter a problem with either of these, the diagnostic scanner will show codes that could lead to the engine shutting down.

A failing G28 sensor here could cause an inaccurate speed counter for your gearbox or a gearbox that shifts faster than normal, and/or an unfire when in the gear. If you are experiencing any of these issues, it is likely that your sensor is failing and should be replaced. They're cheap and easy to find particularly if they're a Bosch unit like ours. Alternatively, the GM version of this part is also more info a good option.

5. Tachometer

A damaged engine sensor could cause a myriad of issues within your vehicle. It is a crucial part of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is rotating. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear. read more It sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU then processes this signal to control fuel, timig and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show around 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 read more and 1995 RS2 ADU, so the best parts could be found in wrecking yards.