This Week s Top Stories About 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 situated at the top of the transmission, above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, just 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 alert to the G5 Tachometer in instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.

If this sensor fails the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or G40).

It's a bit tricky to test because there are several connector pins, and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is at full operation. Examine for signs of coolant or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, while accelerating from the highway paytoll at a high speed I noticed a significant decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. I took out the spark plugs this morning, three were soaked in gasoline, and the fourth was dry. When i crank the engine, there are no sparks i put tissue on the top of each hole in the injector and the 3 that were drenched in gazoline leap out, however the 4th one stays 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 the PID without success. The car will start when the G28 is unplugged and it runs perfectly when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do, as i think i've pretty much eliminated everything else. I'm concerned that i may have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal 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 an extra in a wrecking shop or parts store. It is simple to test them by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). 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 fuel injector timing, replacement key audi etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that could cause engine shut down.

The signs of a failing G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when you are in gear. It is likely that your sensor is failing and requires to be replaced if you encounter any of these signs. The good news is they are very affordable and easily accessible particularly if you're looking at an Bosch unit which is what ours are. Alternatively, the GM version of this unit is also a good option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues in your car. It is an important part of the transmission in your audi a3 replacement key because it relays information to the ECU regarding how fast or slowly the engine of the car is spinning. If the sensor fails, it could affect the performance of the transmission, as well as the other car's components.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU then processes this signal to regulate the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can test 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 on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between those two pins. This is a standard component across the Replacement Key Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.