It s The Ugly Real Truth Of Audi G28

How to Replace an audi q3 key G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate 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 be a sign of a chain stretch or a jumpy chain link in the upper chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

It's a bit tricky to test since there are different connector pins, and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. When the sensor is fully operational, it should read around 1000 ohms. Check for signs of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a significant drop in power. It was like the engine was running out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth one was dry. I placed a tissue over each injector hole, and when I turn the engine on without sparks, the ones with gazoline jump right out. The fourth one remains closed. I tested the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. So i assume the problem is somewhere else.

I also tried to reset the PID without success. The car is able to start when the G28 is not plugged in and it runs perfectly when it is connected however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures 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, as i think i've pretty much ruled out everything else. But i am afraid I might have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is simple to test them - simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the speed and position of the crankshaft to make decisions about timing of the fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

A failing G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, Audi A1 key fob and/or a misfire in the gear. It is possible that the sensor is failing and requires to be replaced if you notice any of these symptoms. They're cheap and easy to find, especially in the case of a Bosch unit like ours. Alternately, GM's version this part would be an excellent choice.

5. Tachometer

A faulty engine speed sensor replacement Audi A3 key could be the cause of a slew of issues in your car. It's a vital component of the audi Q7 key's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can check 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]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is a typical component across the audi connect key 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.