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How to Replace an audi a5 key fob G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located near the edges of the transmission just above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located 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 signals to ECU pin T55/49 through the grey wire. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. 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 needs to know when the crankshaft has reached TDC and also where the camshaft lies so that it can activate 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 could indicate the chain is stretched or a jump link on the upper timing chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

It's a bit tricky to test as there are several 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. If the sensor is operational, it should be reading approximately 1000 ohms. If you're experiencing issues with this sensor, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is running out of gas or injectors aren't firing any more. This morning i pull out the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I crank the engine without sparks i put tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is in another place.

I also tried to reset the PID without success. The replacement audi car key can start when the G28 is disconnected and runs fine when it is plugged in, but still 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. Also, i 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 certain what to do, i think i've pretty much eliminated everything else. However, i'm afraid that I may have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). 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. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will show codes that could cause the engine shutting down.

A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts faster than normal, or a misfire in the gear. It is probable that the sensor is failing and requires to be replaced if you encounter any of these signs. They are cheap and easy-to-find, especially in the case of a Bosch unit like ours. Alternately, GM's version this component is an option.

5. Tachometer

A failing engine sensor could cause a number of problems within your vehicle. It is a crucial part of the audi spare key cost's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor could cause the transmission to fail and other components of the car to be affected.

The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU is then able to process the signal to control fuel, timig, and boost, and also transmitting it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show approximately 1000 ohms of resistance between those points. This is a standard component across the replacement audi a3 key 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.