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How to Replace an audi key shell G28 Engine Speed Sensor

Charles the Humble Technician teaches 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 sends a message to the ECU through the grey wire T55/49 and then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

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

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the location of the camshaft to trigger the spark and injectors.

If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and possibly indicating chain stretch or a jumped 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 challenging because there are two connector pins, and they perform different functions however the best method of testing it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when the sensor is in full operation. Examine for signs of coolant or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had a big cut in power like the engine is out of gas or injectors are not firing at all. I pulled out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. I put tissue over each hole in the injector and when i start the engine with no sparks, audi A3 Key Fob the three with gazoline jump out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero Ohm. So i assume the problem is somewhere else.

I also tried to reset the PID but without success. The car can start when the G28 is unplugged and is running fine when it is connected however it is experiencing intermittent misfires at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I don't know what to do. I believe that I've ruled everything else out. But i am afraid I might have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

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

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the position and speed the crankshaft to determine timing of the fuel injector, 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 lead to engine shutdown.

Some of the signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when you are in gear. It is possible that the sensor is failing and requires to be replaced if you encounter any of these signs. They're cheap and easy to find, especially in the case of a Bosch model like ours. Alternatively, the GM version of this unit is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind many issues in your car. It is a crucial part of the audi q3 key's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is spinning. This sensor can cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. 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 check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This part is common across the Audi a1 key fob 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and 1995 RS2 Du You may also find them in wrecking yards.