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 situated on the edge of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49), then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the outside of the transmission, above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate fuel and boost. It also sends signals to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors in the right way.

If this sensor fails when it fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper timing chain. The code will not appear 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 each one has different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is operating at its maximum. Examine for evidence of coolant or oil in the connector bay if there are problems with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a significant decrease in power. It was like the engine was running out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning, three were drenched in gasoline and the fourth was dry. When i crank the engine, there are no sparks i put tissue on the top of each of the injector holes, the 3 drenched with gazoline leap out, however the 4th stay shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. So i assume the problem is elsewhere.

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

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

3. Fuel Pump

The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80, 100, here 200, UrS and RS2 cars so you can easily find one at a salvage yard or from a parts store. It is simple to test them - just put your DMM into resistance mode and measure read more the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injectors, click here etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either of these, the diagnostic scanner will show codes that could cause an engine shut down.

Some of the signs of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you are in gear. If you experience any of these issues, it is likely that your sensor is deteriorating and needs replacing. The good news is that they are very affordable and easy to find, especially when you're looking at the Bosch unit which is what we have. You can also choose the GM version of this part is also a good choice.

5. Tachometer

A failing engine sensor could cause a variety of issues in your car. It's an essential component of the transmission of your Audi since it sends information to the ECU regarding how fast or slow the engine is turning. 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 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, and also timig. It also transmits it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by examining the continuity from the more info sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and the 1995 RS2 Du You may also find some good ones in wrecking yards.