20 Myths About Audi G28: Dispelled

How to Replace an replacement audi key fob tt audi key fob not working fob (read this blog post from schou-tucker.technetbloggers.de) 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 sends a signal to 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 situated at the edges of the transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends an alert to the G5 Tachometer within the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft 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 not in sync, possibly indicating chain stretch or a jumped link on the upper timing chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).

It is a little tricky to test as there are various pins on the connector, and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when it is operating at its maximum. If you're experiencing issues with this part, check for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power as if the engine was running out of gas or the injectors aren't firing at all. I took out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put a piece of tissue over each injector hole and when i start the engine without sparks, the 3 with gazoline jump out. The 4th one remains closed. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. I'm assuming that the issue is elsewhere.

I also tried to reset the PID without success. The car will start when the G28 is unplugged and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

I'm not certain what to do, but i think i've pretty much ruled out everything else. I'm afraid i may 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 from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a audi spare key replacement in a wrecking shop or a parts store. Testing them is easy 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 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 must be aware of the speed and position of the crankshaft to make a decision about fuel injector timing etc. It uses 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 display codes that could lead to an engine shut down.

The signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. The good news is they are quite affordable and readily available particularly in the case of the Bosch unit which is what ours are. Alternately, GM's version this part is a good option.

5. Tachometer

A failing engine speed sensor could be a cause for a slew of issues with your vehicle. It's a vital component of your programming audi key's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is rotating. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should detect an average resistance of 1000 ohms in these areas. This is a typical component across the audi a3 key 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.