How to Replace an audi a3 key fob replacement G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission over the flywheel gear. It transmits a signal to the ECU through an uncolored wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, just above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors in the right way.

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 chain of timing. The code will not appear without the additional information provided by other sensors (G4 or G40).

Testing is a bit tricky since there are two connector pins, and they serve different purposes but the most effective way to test it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should read approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a significant decrease in power. It was as if the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the 4th was dry. I put tissue over each injector hole and when I turn the engine on without sparks, the 3 that have gazoline pop right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get 0ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. 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 completely ruled out all other possibilities. I'm worried that i might have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal from 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. You can easily locate a spare in a wrecking shop or parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know both the position and speed of the crankshaft to determine timing of the fuel injector, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will display the codes that could trigger an engine shutdown.

A malfunctioning G28 sensor could result in an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, and/or a misfire while in gear. If you have any of these problems, it is most likely that your sensor is deteriorating and requires replacement. They are cheap and easy-to-find, especially when they're a Bosch model like ours. You can also choose the GM version of this component is also a good choice.

5. Tachometer

A failing engine speed sensor could be the cause of many issues in your vehicle. It's a crucial component of the transmission of your audi key because it relays information to the ECU about how fast or slowly the engine of the car is turning. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate the amount of fuel and boost, as well as timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms cost of audi key replacement resistance between these two points. This is a common feature across the audi tt replacement key 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU, so you might find good ones in wrecking yards.