How to Replace an audi a3 spare key G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located on the outside of the transmission, above the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) and 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 G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indication to the G5 Tachometer in instrument cluster.

The sensor is used to correlate the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test because there are various 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 about 1000 ohms if the sensor is at full operation. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a significant drop in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was dry. I put a piece of tissue over each injector hole and when I turn the engine on without sparks, the 3 that have gazoline pop right out. The fourth one remains shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. i get 0ohm. I'm assuming that the issue is elsewhere.

I also tried to reset PID without success. The car can start when the G28 is disconnected and it runs perfectly when it is plugged in however it has intermittent misfire issues at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.

I'm not sure what to do. I feel like i've pretty much all other possibilities out. I'm afraid i may have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80 100 200, car key cover audi UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. It is simple to test them by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed of the crankshaft to make decisions regarding timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go badly, you will see codes on the diagnostic scanner that could cause engine shut down.

A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, and/or a misfire in gear. If you experience any of these issues it is likely that your sensor is going bad and requires replacement. The good news is that they are very affordable and easily accessible, especially if you're looking at an Bosch unit which is what ours are. You can also choose the GM version of this unit is also a good choice.

5. Tachometer

A faulty engine speed sensor could be the cause of a slew of issues with your car. It's an essential component of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is turning. When this sensor fails, it can cause problems for the transmission and the other car Key cover audi's components.

The G5 engine speed sensor is located on the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to control fuel and boost, and also timig. It also relays it to the G5 Tachometer in 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 the resistance to be around 1000 ohms between these points. This is a common component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.