How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is situated on the edge of transmission, directly above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to control the amount of fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.

If this sensor fails, the ECU will display a P00160 error code. 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 jumped chain link in the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).

It's a bit tricky to test as there are various 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. When the sensor is operational, it should be reading about 1000 ohms. Check for signs of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, I experienced an abrupt drop in power as if the engine was running out of gas or the injectors are not firing at all. 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 start the engine without sparks, the ones with gazoline jump right out. The fourth one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get zero ohm. I'm assuming that the issue is somewhere else.

I also tried to reset the PID but with no luck. The car is able to start if the G28 is disconnected and is running fine when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows temperatures of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do. I believe that I've ruled everything else out. I'm concerned 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 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 salvage yard or at a parts store. It is simple to test them - just put your DMM into resistance mode more info and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the position and speed of the crankshaft to make a decision about timing of the fuel injectors, etc. In order 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 one of these, the diagnostic scanner will display the codes that could trigger the engine shutting down.

A failing G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, or a misfire while in gear. If you are experiencing any of these issues it is most likely that your sensor is going bad and requires replacement. The good news is that they are very affordable and easy to find particularly in the case of a Bosch sensor, like ours. Alternately, the GM version of this unit is also a good option.

5. Tachometer

A faulty engine speed sensor could be the cause of numerous problems in your car. It's a vital component of your Audi's transmission, because it communicates to the ECU about how website fast or slow the vehicle's crankshaft is rotating. This sensor could cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located near the edge of the audi replacement car keys transmission, over the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU utilizes this signal to control fuel and boost, as well as timig. It also relays it to the get more info G5 Tachometer inside the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should detect a resistance of approximately 1000 ohms between these two points. This is a common feature across the check here Audi 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 good ones in wrecking yards.