How to Replace an audi lost key G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, just above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and audikey (Instapages.stream) timig. It also sends an indication to the G5 tachometer in the instrument cluster.

The sensor serves as a reference point to connect 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 activate spark and injectors in the right way.

If this sensor fails, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of line with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging since there are two connector pins and they serve different purposes but the best way to test it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is in full operation. If you're experiencing issues with this sensor, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors are not firing anymore. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. When i crank the engine with no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. Therefore, i think the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.

I'm not sure what to do, i believe that i've eliminated everything else. But i am afraid I might have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as 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 from a parts store. Test them out to do - just put your DMM in resistance mode and measure the resistance 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 are equipped with an ECU that has to be aware of the speed and position of the crankshaft to make decisions about timing of the fuel injector, for example. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.

Some of the signs of a failing G28 sensor are an inaccurate rev counter for the gearbox, gears shifting quicker than normal and/or a misfire when in gear. If you are experiencing any of these problems, it is likely your sensor is deteriorating and needs replacing. They're cheap and easy to find particularly if they're an Bosch sensor like ours. Alternately, the GM version of this component is also a good option.

5. Tachometer

A faulty engine speed sensor could be the reason behind a slew of issues in your car. It's an essential component of the transmission in your audi keyless go because it relays information to the ECU regarding how fast or slow the car's engine is turning. If this sensor fails, it will cause problems for the transmission and the rest of the car's components.

The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU is then able to process the signal to control fuel, timig, and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. You can also check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. It should show approximately 1000 ohms resistance between these two points. This is a typical part that is found across the audi key shell 80 100 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.