How to Replace an Audi A1 keys G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is situated at the top of the transmission above the flywheel ring gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer in 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 an electrical signal to ECU pin T55/49 using the grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must 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 an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. However, the code won't appear on its own without additional information from other sensors (G4 and G40).

Testing can be a bit difficult since there are two pins for the connector and they perform different functions but the most effective method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is operating at its maximum. Examine for evidence of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge reduction in power. It was like the engine had run out of gas. Or my injectors were not firing. I pulled out the spark plugs this morning, three were soaked in gasoline, and the 4th was dry. When I crank the engine, there are no sparks i put tissue on the top of each hole in the injector, the 3 drenched with gazoline leap out, however the 4th one stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. Therefore, i think the issue is in another place.

I also tried to reset the PID without success. The car can start when the G28 is disconnected and is running fine when it is connected, but still is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is zero.

I'm not sure what to do. I feel like i've pretty much ruled everything else out. I'm 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 identical to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or parts store. Test them out to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft in order to make decisions about timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.

A damaged G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or an unfire when in gear. It is possible that your sensor is failing and needs to be replaced if you encounter any of these signs. The good news is that they are quite affordable and easily accessible particularly in the case of a Bosch sensor, like ours. If you prefer, GM's version of this part is a good option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues in your car. It is an important part of the transmission of your audi a3 key fob key replacement cost (Highly recommended Website) because it relays information to the ECU on how fast or slowly the engine of the car is spinning. If the sensor fails, it can affect the performance of the transmission as well as the rest of the car's components.

The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to control the amount of fuel and boost, and also timig. It also relays it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also check continuity between pin 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 see approximately 1000 ohms resistance between those two pins. This is a common component across the audi a1 key 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.