20 Myths About Audi G28: Dispelled

How to Replace an audi q3 key G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located near the transmission's edge just above the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control fuel and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC and also the location of the camshaft to trigger the spark and injectors.

If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jump in the chain link of the upper chain. The code won't appear without the additional information provided by other sensors (G4 or G40).

It is a little tricky to test since there are several connector pins, and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is fully operational, it should read around 1000 ohms. If you are having problems with this sensor, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had an abrupt drop in power like the engine is out of gas or injectors aren't firing anymore. Today, i pulled out the spark plugs. Three were drenched in gazoline, the 4th one was dry. I put a piece of tissue over each hole in the injector and when i turn the engine on without sparks, the 3 that have gazoline pop right out. The fourth one remains closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I'm assuming the issue is in another place.

I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue persists at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. Also, programmers i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, but i think i've pretty much ruled out everything else. However, i'm afraid that I may have missed something. Please let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that has to know the position and speed of the crankshaft in order to make decisions about timing of the fuel injectors, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will show codes that could cause an engine shutdown.

The signs of a malfunctioning G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal and/or misfiring when you're in gear. If you have any of these issues it is most likely that your sensor is going bad and requires replacement. The good news is they are very cheap and programmers readily available particularly if you're looking at the Bosch model, which is what we have. If you prefer, GM's version of this component is an option.

5. Tachometer

A faulty engine speed sensor could be the reason behind numerous problems in your vehicle. It is an important part of the transmission of your audi key replacement cost because it relays information to the ECU regarding how fast or slowly the car's engine is turning. This sensor could cause the transmission to malfunction and other components of the car to be affected.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to control fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 and pin T26a/12. You should observe approximately 1000 ohms resistance between these two points. This is a common part across the audi key fob not working 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.