How to Replace an audi key blade G28 Engine Speed Sensor

In this video, Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the edge of transmission just above the flywheel gear. It transmits a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer located in 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 a signal to ECU pin T55/49 via a grey wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends a signal 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 reached TDC and also the position of the camshaft, to trigger the spark and injectors.

If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of a chain stretch or a jump in the chain link of the upper timing chain. The code won't appear without the additional information provided by other sensors (G4 or 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 method for doing this is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is operating at its maximum. Look for evidence of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant drop in power. It was as if 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 was dry. I put a piece of tissue over each hole in the injector and when i turn the engine on without sparks, the three with gazoline jump out. The 4th one remains closed. I tested the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I'm assuming the issue is somewhere else.

I also tried to reset PID but without success. The car can start when the G28 is unplugged and runs fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.

I'm not certain what to do, as i believe that i've completely ruled out all other possibilities. I'm concerned that i may have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by 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 locate an extra 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 at the connector end facing upwards). They should be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to be aware of the position and speed of the crankshaft in order to make a decision about timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.

A damaged G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, or a misfire while in the gear. If you have any of these problems, it is likely your sensor is deteriorating and needs replacing. They are cheap and easy-to-find, especially in the case of a Bosch unit like ours. If you prefer, GM's version of this component is an option.

5. Tachometer

A failing engine sensor could cause a variety of issues in your vehicle. It's a crucial component of the transmission in your audi keyfob a1 key fob (additional hints) because it relays information to the ECU regarding how fast or slowly the car's engine is turning. When this sensor fails, it can cause problems for the transmission, as well as the other car's components.

The G5 engine speed sensor is situated on the outside 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 is then able to process this signal to regulate fuel, timig, and boost, and also transmitting it to the G5 tachometer in the 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 [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should observe approximately 1000 ohms of resistance between those two pins. This is a common component across the replacement audi car key 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.