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How to Replace an replacement audi key fob a5 key for audi fob (sneak a peek here) G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located near the edges of the transmission above the flywheel ring gear. It sends a signal to the ECU via a grey wire (T55/49) and then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located at the edges of the transmission, just above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to control boost and fuel. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.

If this sensor fails, the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain stretching or a jump link on the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test as there are various pins on the connector and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is functional, it should read about 1000 ohms. Look for signs of coolant, or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced massive power loss as if the engine was running out of gas or injectors aren't firing anymore. This morning i pull out the spark plugs, 3 were drenched with gazoline the 4th one was dry. When I crank the engine with no sparks, i place a tissue on the top of each of the injector holes, the 3 drenched with gazoline leap out, however the 4th one stays closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. Therefore, i think the issue is somewhere else.

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

I'm not sure what to do, i feel i have pretty much completely ruled out all other possibilities. But i'm worried that I may have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to 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 junkyard or at a parts store. Testing them is easy - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They should be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft to determine fuel injector timing, etc. To accomplish this, it makes use of 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 lead to engine shutdown.

The signs of a failing G28 sensor are an inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or misfiring when in gear. It is likely that the sensor is failing and requires to be replaced if you encounter any of these signs. The good news is they are very cheap and easy to find, especially if you're looking at a Bosch unit which is what ours are. Alternatively, the GM version of this unit is also a good option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It is an important part of the transmission in your replacement audi key fob because it relays information to the ECU regarding how fast or slow the engine is spinning. This sensor could cause the transmission to fail and other components in the audi car key to be affected.

The G5 engine speed sensor is located on the outside of the transmission above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU uses this signal to control the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see the resistance to be around 1000 ohms between these two points. This is a standard component across the audi q3 key 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.