How to Replace an audi keyless go 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 transmits a signal to the ECU via the grey wire T55/49 and then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the outside of the transmission, just above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to control fuel and boost. It also sends a signal to the G5 tachometer inside the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors accordingly.

If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

It is a little tricky to test since 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. It should read around 1000 ohms when it is operating at its maximum. If you're experiencing issues with this sensor, look for evidence of oil or Audi a3 key Fob coolant in the connector bay.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced a big cut in power as if the engine was running out of gas or injectors aren't firing any more. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was dry. I put a piece of tissue over each injector hole and when i start the engine without sparks, the three with gazoline jump right out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. I'm assuming the issue is elsewhere.

I also tried to reset the PID but 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 the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.

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

3. Fuel Pump

The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is similar 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 parts store. It is simple to test them - simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make a decision about fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go bad you will get codes on the diagnostic scanner that could cause engine shut down.

Some of the signs of a failed G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal, and/or a misfire when you're in gear. If you have any of these problems, it is likely your sensor is going bad and needs replacing. The good thing is that they are very cheap and readily available, especially if you're looking at a Bosch sensor, which is what ours are. Alternately, GM's version this part is an option.

5. Tachometer

A damaged engine sensor could cause a myriad of issues within your vehicle. It's an essential component of your audi a3 spare key's transmission, because it communicates 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 directly to the ECU at pin T55/49 via an uncolored wire. The ECU then uses and processes this signal to regulate fuel, timig, and boost as well as transmitting 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 verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and cost between pin T6a/1 as well as pin T26a/12. You should see around 1000 ohms of resistance between those points. This part is common across the audi a1 key 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du So, you may find some good ones in wrecking yards.