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How to Replace an audi keys G28 Engine Speed Sensor

Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is located at the top of the transmission just above the flywheel ring gear. It sends a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer within the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. 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 is used to correlate with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.

If this sensor fails when it fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate a chain stretch or a jumped chain link in the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging because there are two connector pins, and they perform different functions however the best method to test it is to measure resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is operating at its maximum. Check for signs of coolant, or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge drop in power. It was like the engine had run out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, 3 were soaked in gasoline, Audi A1 Key Fob and the 4th was dry. I put a piece of tissue over each hole in the injector and when i start the engine with no sparks, the 3 with gazoline jump out. The fourth one remains closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I found zero ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID with no success. The car will start if the G28 is not plugged in and is running fine when it is connected however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. Also i 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, i believe that i've ruled out everything else. But i am afraid I may have missed something. Please let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is the same as the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is simple to test them to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black end of the connector). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft in order to make a decision about timing of the fuel injectors, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these, the diagnostic scanner will display codes that could lead to an engine shutdown.

A failing G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts faster than normal, or an unfire when in gear. If you have any of these issues, it is likely that your sensor is deteriorating and requires replacement. The good news is that they are very cheap and easily accessible, especially if you're looking at a Bosch model, which is what ours are. You can also choose the GM version of this component is also a good option.

5. Tachometer

A failing engine speed sensor could be the cause of a slew of issues in your car. It's a crucial component of the transmission in your Audi A1 keys since it sends information to the ECU about how fast or slow the car's engine is turning. If this sensor fails, it could disrupt the performance of the transmission as well as the rest of the car's components.

The G5 engine speed sensor is located on the outside of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via a grey wire. The ECU then uses and processes this signal to regulate fuel, timig and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can check 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 on pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between these two points. This part is common across the Audi key fob not Working (g28carkeys54558.ageeksblog.com) 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU So, you may find some good ones in wrecking yards.