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How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician shows how to replace audi key the G28 Engine Speed Sensor. This sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via the grey wire (T55/49), then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors accordingly.

If this sensor fails, the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain is stretched or a jump 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 can be a bit difficult to test as there are various pins on the connector and they all have different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is operating at its maximum. If you are having problems with this part, check for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a massive reduction in power. It was as if 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 fourth one was dry. I placed a tissue over each hole in the injector and when I start the engine with no sparks, the 3 that have gazoline pop right out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. I assume that the problem is in another location.

I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The coolant sensor (G62), even when unplugged, still shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.

I don't know what to do. I feel like i've pretty much all other possibilities out. However, i'm afraid that I might have missed something. Let me know If 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 similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or a parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either one of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.

The signs of a failing G28 sensor include an inaccurate rev counter for the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is possible that your sensor is failing and requires to be replaced if you notice any of these symptoms. They are cheap and easy-to-find particularly when they're a Bosch unit like ours. Alternatively, the GM version of this unit is also a good choice.

5. Tachometer

A damaged engine sensor could cause a number of problems in your car. It's an essential component of the audi a5 key audi fob (Resource)'s transmission since it relays information to the ECU about how fast or slow the car's crankshaft is turning. When this sensor fails, it could affect the performance of the transmission as well as the other car's components.

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