How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician shows 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 through a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, above the flywheel ring. The sensor sends a signal via the grey wire to pin T55/49. audi a4 key replacement utilizes this information to regulate the boost, fuel, and timig. It also sends signals to the G5 tachometer in the instrument cluster.

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

If this sensor fails when it fails, the ECU will display a P00160 error code. 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 jump in the chain link of the upper timing chain. However, the error code won’t be displayed on its own without additional information from other sensors (G4 and G40).

It can be a bit difficult to test since there are several connector pins, and each one has different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is operating at its maximum. If you’re having issues with this sensor, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced a big cut in power like the engine is running out of gas or injectors are not firing at all. In the morning, i removed the spark plugs, three were soaked with gazoline and the fourth one was dry. I put tissue over each hole in the injector and when I start the engine without sparks, the three that have gazoline pop right out. The 4th one remains shut. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. audi a4 spare key think the issue is somewhere else.

I also tried to reset the PID but with no luck. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar when the actual pressure is 0.

I’m not sure what to do. I believe that I’ve eliminated everything else. I’m worried that i might have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a salvage yard or from a parts store. It is easy to test them – simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector’s edge facing upwards). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know both the speed and position of the crankshaft to determine fuel injector timing, etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown.

Some of the signs of a malfunctioning G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal, and/or a misfire when you’re in gear. It is likely that your sensor is failing and needs to be replaced if you encounter any of these signs. They’re inexpensive and easy to locate, especially if they’re an Bosch model like ours. You can also choose the GM version of this unit is also a good choice.

5. Tachometer

A failing engine speed sensor could be the reason behind many issues in your vehicle. It’s a crucial component of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slowly the engine is turning. This sensor could cause the transmission to fail and other components of the car to be affected.

The G5 engine speed sensor is situated on the outside of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU utilizes this signal to control fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between these two points. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.