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How to Replace an audi key Fob not working G28 Engine Speed Sensor

In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is situated near the edges of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer in 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 a signal to ECU pin T55/49 through the grey wire. The ECU uses this information to control boost and fuel. It also sends signals to the G5 tachometer in the instrument cluster.

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

If this sensor fails, the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating chain stretch or a jumped link on the upper timing chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).

It's a bit tricky to test as there are several pins on the connector and each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read around 1000 ohms. Look for signs of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a significant decrease in power. It was like the engine was running out of gas. Or, my injectors were not firing. Today, i pulled out the spark plugs, three were soaked with gazoline and the 4th one was dry. When I start the engine, there are no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stay shut. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I assume that the problem is in another location.

I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I'm not certain what to do, as i think i've pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! 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 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find the spare in a salvage shop or parts store. Testing them is easy to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's end). They must be infinite ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines needs to know both the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go wrong, you will receive codes on the diagnostic scanner which could cause engine shut down.

The signs of a failed G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when you're in gear. It is possible that the sensor is failing and requires to be replaced if you experience any of these signs. The good thing is that they are very cheap and easily accessible particularly if you're looking at the Bosch sensor, which is what ours are. Alternatively, the GM version of this unit is also a great option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your car. It is an important part of the transmission of your audi key programmer, as it transmits information to the ECU regarding how fast or slow the car's engine is spinning. This sensor could cause the transmission to malfunction and costs other components of the car to be affected.

The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to control the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer in 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 and pin T26a/12. You should observe around 1000 ohms of resistance between those points. This part is common across the audi q7 key 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU, so you might find some good ones in wrecking yards.