How to Replace an audi a1 car key G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace audi key fob the G28 engine speed sensor. This sensor is situated on the outside of the transmission just above the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.

1. Engine Speed Sensor

The grey wire is located at the edges of the transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then utilizes this information to regulate the flow of fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.

If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jump in the chain link of the upper chain of timing. However, the error code won't appear on its own without additional information from other sensors (G4 and 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 resistance between the sensor and the ECU. It should read around 1000 ohms when it is in full operation. Look for signs of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced an abrupt drop in power as if the engine was running out of gas or the injectors are not firing any more. I took out the spark plugs this morning, 3 were drenched in gasoline and the fourth was dry. I put tissue over each hole in the injector and when I start the engine without sparks, the three with gazoline jump right out. The 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. So i assume the problem is elsewhere.

I also tried to reset the PID but without success. The car will start when the G28 is unplugged and it runs perfectly when it is connected however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.

I'm not certain what to do, i think i've pretty much completely ruled out all other possibilities. But i'm worried that i might have missed something. If anyone has any ideas please let me know! 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, programming audi key 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 - 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 side). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to be aware of the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injector, for example. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, and/or a misfire while in the gear. It is possible that the sensor is failing and requires to be replaced if you notice any of these signs. The good news is they are very cheap and readily available particularly when you're looking at an Bosch sensor, which is what ours are. Alternately, the GM version of this part is also a good choice.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of issues in your car. It is a crucial part of your audi new key's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. If this sensor fails, it will disrupt 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. It transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU is then able to process this signal to control 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 examining the continuity from the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see approximately 1000 ohms of resistance between those points. This is a typical part that is found across the audi tt key 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.