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How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic 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 to the ECU via a grey wire T55/49, then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 through an uncolored wire. The ECU uses this information to regulate boost and fuel. It also sends an indication to the G5 tachometer in the instrument cluster.

The sensor is used to link the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.

If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't show without the additional information provided by other sensors (G4 or G40).

It is a little tricky to test as there are various pins on the connector and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms if the sensor is at full operation. Examine for signs of coolant, or oil in the connector bay if you have problems with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had a big cut in power like the engine is out of gas or the injectors aren't firing any more. This morning i pull out the spark plugs, three were soaked with gazoline and the 4th one was dry. When I crank the engine, there are no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th stays closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get 0ohm. So i assume the problem is in another place.

I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem persists 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 when the actual pressure is 0.

I'm not sure what to do. I feel like i've pretty much eliminated everything else. But i'm worried that I may have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump on the g28 is activated by a signal by the RPM sensor. The GM-style transmitter functions similarly to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find the spare in a salvage shop or parts store. It is simple to test them by putting 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 of our 20vt turbo (3B AAN ABY ADU) engines requires to know both the position and speed the crankshaft to make decisions regarding timing of fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If article source have a problem with either one of these, the diagnostic scanner will display codes that could cause the engine shutting down.

A failing G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, and/or a misfire in the gear. If you have any of these issues, it is likely that your sensor is failing and needs replacing. They're cheap and easy to find particularly in the case of an Bosch model like ours. Alternately, GM's version this part is an excellent choice.

5. Tachometer

A failing engine sensor could cause a myriad of issues in your vehicle. It's an essential component of the transmission in your Audi because it relays information to the ECU on how fast or slowly the engine of the car is spinning. If the sensor fails, it can affect the performance of the transmission as well as the rest of the car's components.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It transmits a signal via an uncolored wire to the ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig and boost as well as sends it on to the G5 tachometer in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 Du So, you may find some good ones in wrecking yards.

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Pub: 18 Mar 2024 06:17 UTC
Views: 36