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 on the edge 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 located on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via the grey wire. The ECU then utilizes this information to regulate fuel, timig 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 must know when the crankshaft is TDC and where the camshaft is so it can activate spark and injectors according to the situation.

If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, 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 different pins on the connector, and each one has different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. When the sensor is fully functional, it should read around 1000 ohms. If you are having problems with this part, check for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at maximum speed, i noticed a huge decrease in power. It was like the engine had run out of gas. Or my injectors weren't firing. This morning i pull out the spark plugs. Three were drenched in gazoline, the fourth one was dry. When I crank the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th one stays shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID but with no luck. The car is able to start if the G28 is not plugged in and is running fine when it is connected but it still has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.

I don't know what to do. I believe that I've eliminated everything else. I'm concerned that i may have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or in a local parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

A failing G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, and/or a misfire in the gear. If you are experiencing any of these issues, it is likely that your sensor is going bad and needs replacing. The good thing is that they are very affordable and easy to find particularly when you're looking at the Bosch model, which is what we have. If you prefer, GM's version of this part would be an option.

5. Tachometer

A malfunctioning engine sensor can cause a myriad of issues in your car. It's a vital component of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. This sensor could cause the transmission to malfunction and other car components to be affected.

The G5 engine speed sensor is located at the edge of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to control the flow of fuel and boost as well as timig. It also sends it to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms of resistance between those two pins. This part is common across the audi key tt replacement audi a4 key key (read the full info here) 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 DU You may also find good ones in wrecking yards.