How to Replace an Audi A3 Key Fob Replacement G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located near the transmission's edge over the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 through the grey wire. The ECU utilizes this information to control boost and fuel. It also sends an indicator to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft reached TDC, and the position of the camshaft, to trigger the spark and injectors.

If this sensor fails the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain stretching or Audi a3 key Fob Replacement a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).

It's a bit tricky to test because there are various pins on the connector and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is at full operation. If you're having issues with this component, look for signs of oil or coolant in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at a high speed I noticed a massive reduction in power. It was as if the engine was running out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. I placed a tissue over each hole in the injector and when i turn the engine on without sparks, the ones with gazoline jump right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I'm assuming the issue is elsewhere.

I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it works fine when the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I'm not sure what to do. I believe that I've ruled everything else out. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a 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 end facing upwards). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that must know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injectors, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.

A malfunctioning G28 sensor could cause an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, or a misfire while in the gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these signs. The good thing is that they are quite affordable and easy to find particularly when you're looking at the Bosch sensor, which is what we have. Alternately, the GM version of this part is also a good option.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems within your vehicle. It's an essential component of the transmission in your audi key fob replacement since it sends information to the ECU regarding how fast or slow the engine is turning. This sensor can cause the transmission to fail and other components in 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 transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU then processes this signal to regulate the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can test for sensor 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 [79trace [79]) and between pin T6a/1 and pin T26a/12. There should be an average resistance of 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 model, ranging beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU, so you might find them in wrecking yards.