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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 over the flywheel gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer on 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 a grey wire. The ECU utilizes this information to control boost and fuel. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference replacement key for audi comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC and also where the camshaft lies in order to activate the spark and injectors.

If this sensor fails the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't show without the additional information provided by other sensors (G4 or G40).

Testing is a bit challenging as there are two different connector pins, and they perform different functions but the most effective method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is operational, it should be reading around 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a massive reduction in power. It was like the engine had run out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs, 3 were drenched with gazoline the fourth one 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 closed. I checked the ground connection of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is elsewhere.

I also tried to reset the PID with no success. The car can start when the G28 is not plugged in and runs fine when it is plugged in but it still has intermittent misfire issues at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

I'm not certain what to do, as i feel i have pretty much eliminated everything else. But i'm worried that i might have missed something. If anyone has any ideas please chime in! 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 and both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. Testing them is easy to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know both the position and speed of the crankshaft to determine timing of fuel injectors, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either one of these, the diagnostic scanner will show codes that could lead to an engine shut down.

Some of the signs of a failing G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when you are in gear. If you are experiencing any of these issues it is most likely that your sensor is deteriorating and needs replacing. They're inexpensive and easy to locate particularly if they're an Bosch model like ours. Alternately, the GM version of this component is also a great option.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of issues with your car. It's a vital component of the Audi A1 keys's transmission because it communicates to the ECU about how the car's crankshaft is rotating. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms resistance between these two points. This is a typical part that is found across the audi Tt key fob 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.