How to Replace an Audi A1 keys G28 Engine Speed Sensor

Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is located at the edge of transmission, above the flywheel gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, just above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can start spark and injectors in the right way.

If this sensor fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of 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).

Testing is a bit challenging since there are two pins for the connector and they have different functions but the best method of testing it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. Check for signs of coolant, or oil in the connector bay if you are experiencing issues with this component.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced an abrupt drop in power like the engine is running out of gas or the injectors are not firing any more. Today, i pulled out the spark plugs. Three were drenched with gazoline the 4th one was dry. When i crank the engine without sparks, i place a tissue on the top of each of the injector holes and the 3 drenched with gazoline pop out, but the 4th stay closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I think the issue is in another location.

I also tried to reset the PID but with no luck. The car will start if the G28 is unplugged and it runs perfectly when it is connected however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do, i think i've pretty much ruled out everything else. I'm concerned that i may have missed something. If anyone has any ideas please share them! TIA!

3. Fuel Pump

The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. Testing them is easy to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black end of the connector). They should be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines have an ECU that has to know the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could cause the engine shutting down.

A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, and/or a misfire while in the gear. If you have any of these issues it is most likely that your sensor is going bad and should be replaced. The good news is that they are very affordable and easily accessible, especially if you're looking at the Bosch model, which is what we have. Alternately, Audi Replacement Key Service Near Me the GM version of this unit is also a great option.

5. Tachometer

A damaged engine sensor could cause a number of problems in your car. It is an important part of the transmission in your audi tt key fob, as it transmits information to the ECU regarding how fast or slowly the car's 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 located on the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU uses this signal to regulate the amount of fuel and boost, and also timig. It also sends it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see the resistance to be around 1000 ohms in these areas. This is a typical part that is found across the audi Replacement key service near me 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.