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How to Replace an audi advanced key G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is situated on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU via the grey 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 just above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must be aware of 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 when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper chain. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).

It's a bit tricky to test since there are various connector pins, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. If the sensor is operational, it should be reading around 1000 ohms. Examine for signs of coolant or oil in the connector bay if you have issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at a high speed, i noticed a huge decrease in power. It was as if the engine was running out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs. Three were soaked with gazoline and the 4th one was dry. When I crank the engine, there are no sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stay shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero ohm. I'm assuming that the issue is somewhere else.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.

I'm not sure what to do, as i think i've pretty much ruled out everything else. But i'm worried that I might have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter 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 salvage yard or at a parts store. It is simple to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite ohms.

4. ECU

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

A failing G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or a misfire in the gear. If you have any of these problems, it is likely your sensor is going bad and should be replaced. The good news is they are very affordable and readily available particularly if you're looking at a Bosch sensor, like ours. Alternately, the GM version of this unit is also a good option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your car. It's a vital component of the audi a3 key's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to fail and other car components 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 to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to control the flow of fuel and boost and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can check for sensor failure by examining the continuity of the sensor to the tachometer. Also, you can 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. It should show around 1000 ohms of resistance between these two points. This is the same across the audi replacement key service 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU, audi Replacement Key service so you might find them in wrecking yards.