How to Replace an Audi A1 keys G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission just above the flywheel ring gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using the grey wire. The ECU utilizes this information to regulate fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies to trigger the spark and injectors.

If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

It's a bit tricky to test because there are different pins on the connector, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms when it is at full operation. If you are having problems with this part, check for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power like the engine is out of gas or injectors aren't firing any more. Today, i pulled out the spark plugs. Three were soaked with gazoline and the fourth was dry. When I crank the engine with no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 that were drenched in gazoline jump out but the 4th stay shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. So i assume the problem is in another place.

I also tried to reset the PID without success. The car can start if the G28 is unplugged and runs fine when it is plugged in however it has the intermittent misfire issue at higher RPM. The temperature sensor for the 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 bar when the actual pressure is 0.

I don't know what to do. I feel like i've pretty much all other possibilities out. I'm worried that i might have missed something. If anyone has suggestions, please let me know! 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 works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or a parts store. It is easy to test them - just put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the speed and position of the crankshaft to make decisions regarding fuel injector audi Tt replacement Key timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes bad you will get codes on the diagnostic scanner that can cause the engine to shut down.

The signs of a malfunctioning G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when you are in gear. If you experience any of these issues it is most likely that your sensor is deteriorating and needs replacing. The good thing is that they are very cheap and easy to find, especially if you're looking at the Bosch unit which is what ours are. Alternatively, GM's version of this component is an excellent choice.

5. Tachometer

A failing engine speed sensor could be a cause for numerous issues in your vehicle. It is an important part of the transmission of your replacement audi key since it sends information to the ECU regarding how fast or slow the car's engine is turning. If the sensor fails, it could disrupt the performance of the transmission as well as the other car's components.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via an uncolored wire to the ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This is the same across the audi tt replacement key 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU So, you may find good ones in wrecking yards.