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How to replace audi key fob an programming Audi key G28 Engine Speed Sensor

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

1. Engine Speed Sensor

Located on the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft 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 an error code P00160. This indicates that the Crank Shaft is not in line 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 provided by other sensors (G4 or G40).

It is a little tricky to test because there are various pins on the connector and each has its own 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 when it is in full operation. Check for signs of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced massive power loss as if the engine was running out of gas or the injectors aren't firing at all. This morning i pull out the spark plugs, three were soaked with gazoline and the fourth was dry. When I crank the engine, there are no sparks, i place a tissue on the top of each hole in the injector and the 3 that were drenched in gazoline leap out, however the 4th stay closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I assume that the problem is elsewhere.

I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue persists 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 while the actual pressure is zero.

I'm not certain what to do, i feel i have pretty much ruled out everything else. However, i'm afraid that i might have missed something. Please 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 from the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. Test them out to do - just put 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 side). They must be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will show the codes that could trigger an engine shut down.

A malfunctioning G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. It is possible that the sensor is failing and needs to be replaced if you experience any of these symptoms. They're cheap and easy to find, especially in the case of a Bosch sensor like ours. You can also choose the GM version of this component is also a good option.

5. Tachometer

A damaged engine sensor could cause a myriad of issues in your car. It's a vital component of your audi car key case's transmission, as it sends information to the ECU about how fast or slow the car's crankshaft is turning. When this sensor fails, it will affect the performance of the transmission and the rest of the car's components.

The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to regulate fuel and boost, and also timig. It also sends it to the G5 Tachometer in instrument cluster. You can check key for audi sensor failure by examining the continuity of the sensor to the tachometer. You can also verify 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. You should detect a resistance of approximately 1000 ohms in these areas. This is a common part across the audi key programming 80, 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.