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How to Replace an Audi Q3 key G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends a signal to the G5 tachometer inside the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft has reached TDC, and the location of the camshaft so that it can activate the spark and injectors.

If this sensor fails when it fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of sync 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 of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).

It is a little tricky to test as there are several pins on the connector, and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should read approximately 1000 ohms. Look for signs of coolant, or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed I noticed a significant decrease 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 and key for audi found that 3 were soaked in gasoline, and the fourth was unclean. I put tissue over each injector hole and when i start the engine with no sparks, the ones with gazoline jump right out. The 4th one stays closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I'm assuming that the issue is in another location.

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

I'm not certain what to do, but i believe that i've completely ruled out all other possibilities. But i'm worried that I may have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. It is easy to find an extra in a wrecking shop or parts store. Test them out - 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 end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could lead to an engine shut down.

Some of the signs of a failing G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when you are in gear. If you have any of these issues 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. Alternatively, GM's version of this component is a good option.

5. Tachometer

A failing engine sensor could cause a number of problems in your car. It is a crucial part of the audi key copy's transmission since it relays information to the ECU about how fast or slow the audi replacement car keys's crankshaft is turning. If this sensor fails, it will affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to control fuel and boost, as well as timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in 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 [79trace [79]), and between pin T6a/1 and pin T26a/12. You should see around 1000 ohms of resistance between these two points. This is a standard component across the audi keyless go 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones could be available in wrecking yards.