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

In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated on the outside of the transmission just above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.

1. Engine Speed Sensor

It is located on the outside of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 through a grey wire. The ECU uses this information to control the amount of fuel and boost. It also sends signals to the G5 tachometer in the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC and also the location of the camshaft in order to activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumped chain link in the upper chain. The code will not appear without the additional information provided by other sensors (G4 or audi a3 replacement key G40).

Testing is a bit tricky since there are two connector pins, and they perform different functions but the best way to test it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. If you are having problems with this component, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced a big cut in power like the engine is out of gas or the injectors are not firing at all. I pulled out the spark plugs this morning, three were soaked with gasoline and the fourth was unclean. I put tissue over each injector hole, and when I start the engine without sparks, the three with gazoline jump out. The 4th one stays shut. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I think the issue is elsewhere.

I also tried to reset PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.

I don't know what to do. I believe that I've all other possibilities out. I'm concerned that i may have missed something. If anyone has any suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender is identical to the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's 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 has to know the position and speed of the crankshaft in order to make decisions about timing of the fuel injector, for example. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either one of these, the diagnostic scanner will display codes that could cause an engine shutdown.

A malfunctioning G28 sensor can cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or a misfire in the gear. If you have any of these problems, it is likely your sensor is deteriorating and needs replacing. They are cheap and easy-to-find especially in the case of an Bosch unit like ours. Alternately, the GM version of this component is also a great option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your vehicle. It's an essential component of your Audi's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located at the edge of the transmission, just above the flywheel ring. It sends an electrical signal through a gray wire to the ECU pin T55/49. The ECU is then able to process this signal to regulate fuel, timig, and boost, and also transmitting it to the G5 tachometer inside the instrument cluster. You can test for sensor failure by examining the continuity of 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. You should detect an average resistance of 1000 ohms in these areas. This is a common feature across the replacement audi key fob 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU So, you may find good ones in wrecking yards.