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How to Replace an audi q7 key G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is situated on the edge of the transmission, above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer located in 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 a grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC and also where the camshaft lies in order to activate the spark and injectors.

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

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

2. Injectors

Yesterday, Audi Key Fobs when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was like the engine had run out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the ones with gazoline jump right out. The fourth one remains closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. I assume that the problem is elsewhere.

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

I'm not sure what to do, i believe that i've ruled out everything else. I'm worried that i might have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80 100, 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. Testing them is easy - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's end). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to be aware of the position and speed of the crankshaft to make decisions regarding timing of fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

The signs of a failing G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when in gear. It is probable that the sensor is failing and needs to be replaced if you notice any of these signs. They're inexpensive and easy to locate particularly in the case of a Bosch model like ours. Alternately, the GM version of this part is also a good option.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous issues with your vehicle. It's an essential component of the transmission of your Audi A1 keys, as it transmits information to the ECU on how fast or slow the engine of the car is turning. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU utilizes this signal to regulate the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should detect an average resistance of 1000 ohms between these two points. This is a common component across the audi q7 replacement key 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.