How to Replace an audi key fobs G28 Engine Speed Sensor

In this video Charles the Humble Mechanic demonstrates how to replace audi key the G28 engine speed sensor. The sensor is located near the transmission's edge just above the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster.

Porsche-New-2023.png1. Engine Speed Sensor

The grey wire is located on the edge of transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to know when the crankshaft has reached TDC, and the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumped chain link in the upper chain. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).

It can be a bit difficult to test because there are different pins on the connector and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is at full operation. Check for signs of coolant, or oil in the connector bay if you have issues with this component.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum 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. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. When I crank the engine, there are 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 of ECU pins 14,30, and 48/55. I found zero ohm. I assume that the problem is somewhere else.

I also tried to reset PID without success. 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 temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.

I'm not certain what to do, as i think i've pretty much eliminated everything else. I'm afraid i may have missed something. Please let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or a parts store. It is simple to test them - just switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing up). They should be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines must know both the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either of these sensors, the diagnostic scanner will show codes that could cause an engine shut down.

Some of the signs of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal, and/or a misfire when in gear. It is probable that your sensor is failing and needs to be replaced if you experience any of these signs. They're inexpensive and easy to locate particularly when they're an Bosch sensor like ours. Alternatively, the GM version of this unit is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind numerous issues in your vehicle. It's a crucial component of the transmission of your Replacement Key audi since it sends information to the ECU on how fast or slow the engine is spinning. This sensor could cause the transmission to fail and 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 and sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU uses this signal to regulate fuel and boost, as well as timig. It also sends it to the G5 Tachometer in instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show around 1000 ohms of resistance between those points. This is a common part across the audi spare key replacement 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.

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