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

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located on the outside of the transmission, above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer within the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.

If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jumpy chain link in the upper timing chain. However, the code won’t appear on its own, without additional information from other sensors (G4 and G40).

It’s a bit tricky to test because there are several pins on the connector, and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is at full operation. Examine for evidence of coolant or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the ones with gazoline jump out. The 4th one stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. I assume that the problem is elsewhere.

I also tried to reset PID but without success. The car is able to start when the G28 is not plugged in and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.

I’m not sure what to do. I feel like i’ve pretty much all other possibilities out. I’m afraid i may have missed something. If anyone has any ideas please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style transmitter functions similarly 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 parts store. Test them out – put your DMM in resistance mode and measure between pins 1 (with the bump on the connector’s end up) and 2 (2nd from the left on the black end of the connector). They should be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines must be aware of the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner which can cause the engine to shut down.

A failing G28 sensor could result in an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, or a misfire while in the gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these signs. The good news is that they are very affordable and easily accessible particularly when you’re looking at an Bosch unit like ours. Alternatively, GM’s version of this part would be an excellent choice.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems within your vehicle. It’s a crucial component of the transmission of your audi new key since it sends information to the ECU on how fast or slowly the engine of the car is spinning. If this sensor fails, it can cause problems for the transmission, as well as the other car’s components.

The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also relays 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 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 see an average resistance of 1000 ohms in these areas. This part is common across the audi Tt replacement Key 80-100-200-RS2 series, audi Tt replacement key starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU So, you may find some good ones in wrecking yards.