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How to Replace an audi a3 spare key G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated at the edge of transmission, above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer 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 signals to ECU pin T55/49 via the 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 located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors according to the situation.

If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit tricky since there are two pins for the connector and they perform different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is in full operation. If you're experiencing issues with this sensor, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at maximum speed, i noticed a huge drop in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning, three were drenched in gasoline and the 4th was dry. I put 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 tried to test the ground connections of ECU pins 14,30, and 48/55. I found 0ohm. I'm assuming that the issue is elsewhere.

I also tried to reset the PID with no success. The car will start when the G28 is not plugged in and runs fine when it is plugged in however it has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also 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 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 ideas please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or parts store. It is simple to test them - just switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms.

4. ECU

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

Some of the symptoms of a failing G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal, and/or a misfire when you are in gear. If you experience any of these issues, it is likely that your sensor is failing and requires replacement. They're cheap and easy to find especially if they're an Bosch sensor like ours. If you prefer, Audi Replacement Key Service Near Me GM's version of this part is an option.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems in your car. It is a crucial part of your audi car key case's transmission, as it sends information to the ECU about how the car's crankshaft is rotating. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via a grey wire. The ECU uses this signal to control the amount of fuel and boost, as well as timig. It also relays it to the G5 Tachometer in instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. It should show approximately 1000 ohms of resistance between these two points. This is a typical component across the Audi Replacement Key Cost 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.