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How to Replace an Replacement audi key Fob 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 just above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an alert to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.

If this sensor 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 an issue with the chain or a jump in the chain link of the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).

Testing is a bit tricky because there are two connector pins and they perform different functions but the most effective method to test it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when it is at full operation. Examine for signs of coolant, or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced massive power loss like the engine is out of gas or the injectors are not firing anymore. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the fourth was dry. When i crank the engine without sparks, I put a piece of tissue on the top of each of the injector holes and 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 got zero Ohm. I think the issue is in another location.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, as i believe that i've completely ruled out all other possibilities. However, i'm afraid that I might have missed something. Let me know should you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is simple to test them: simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft to make a decision about timing of the fuel injectors, audi Tt Key programming etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either one of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.

Some of the signs of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when in gear. If you have any of these issues it is likely that your sensor is failing and needs replacing. The good news is they are very affordable and easy to find particularly when you're looking at an Bosch sensor, which is what ours are. Alternately, the GM version of this unit is also a good choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues within your vehicle. It is a crucial part of your audi key programmer's transmission, since it relays information to the ECU about how the car's crankshaft is turning. 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 transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to regulate the flow of fuel and boost as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms resistance between those points. This is a common feature across the audi q5 key 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 DU So, you may find them in wrecking yards.