The Three Greatest Moments In Audi G28 History 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 on the instrument cluster.


1. Engine Speed Sensor

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

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft reached TDC, and where the camshaft lies to trigger the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error code. This means that the Crank Shaft is out of alignment with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumped chain link in the upper chain. The code will not appear without the additional information provided by other sensors (G4 or G40).

It's a bit tricky to test because there are different pins on the connector, and they all have different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read around 1000 ohms. If you are having problems with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at full speed I noticed a massive decrease in power. It was like the engine had run out of gas. Or, audi a4 key replacement were not firing. In the morning, i removed the spark plugs, 3 were drenched in gazoline, the fourth was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the ones with gazoline jump right out. The 4th one stays closed. I tested the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. I think the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it runs fine with the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the gauge for oil pressure in the cockpit is showing 2 bar while the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do, but i think i've pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. Please 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 sender 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 salvage yard or from a parts store. It is simple to test them to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's end). They must be infinite ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to know the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these sensors go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.

Some of the signs of a failed G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you are in gear. If you are experiencing any of these issues it is likely that your sensor is deteriorating and needs replacing. They are cheap and easy-to-find particularly if they're a Bosch model like ours. Alternately, the GM version of this part is also a great option.

5. Tachometer

A failing engine speed sensor could be the reason behind a slew of issues in your car. It's a crucial component of the transmission in your Audi because it relays information to the ECU regarding how fast or slowly the car's engine is spinning. When this sensor fails, it will cause problems for the transmission as well as the other car's components.

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 then processes this signal to regulate fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms between these points. This is a typical part across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.