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 near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) and then to the tachometer in the instrument cluster.

1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using a grey wire. The ECU utilizes this information to regulate boost and fuel. It also sends an indication to the G5 tachometer inside the instrument cluster.

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).

It is a little tricky to test since there are different pins on the connector and they all have different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms when the sensor is at full operation. If you are having problems with this sensor, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss as if the engine was running out of gas or injectors are not firing at all. This morning i pull out the spark plugs, three were drenched with gazoline the fourth was dry. When I crank the engine, there are no sparks, i place a tissue on the top of each of the injector holes and the 3 that were drenched in gazoline jump out but the 4th stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. I think the issue is in another location.

I also tried to reset the PID with no success. The car will start when the G28 is unplugged, and it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of -49c, even if I unplug it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.

I don't know what to do. I feel like i've pretty much all other possibilities out. But i'm worried that I may have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both are used in the 80 100, 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. Test them out - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black end of the connector). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed the crankshaft to make decisions regarding timing of fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go bad you will get codes on the diagnostic scanner which can cause the engine to shut down.

A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or replacement a misfire in gear. If you have any of these issues, it is likely your sensor is going bad and requires replacement. They are cheap and easy-to-find particularly when they're an Bosch sensor 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 cause of many issues in your car. It's an essential component of the transmission of your audi key replacement cost since it sends information to the ECU on how fast or slow the engine is turning. This sensor can cause the transmission to fail and other components of the car to be affected.

The G5 engine speed sensor is situated on the edge of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to control fuel and boost, and also to timigrate. It also sends it to the G5 Tachometer located in the 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 on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between these two points. This is the same across the audi advance key 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du, so you might find some good ones in wrecking yards.