Notes

Why You Should Concentrate On The Improvement Of Audi G28
How to Replace an Audi G28 Engine Speed Sensor

In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located at the top of the transmission, above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49) which is then sent 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. The sensor transmits signals through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to connect the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC, and the location of the camshaft to trigger the spark and injectors.

If this sensor fails when it fails, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of a chain stretch or a jumped chain link in the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).

It is a little tricky to test because there are different connector pins, and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when the sensor is operating at its maximum. Check for signs of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge decrease in power. It was like the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning, three were soaked with gasoline and the fourth was dry. I placed a tissue over each injector hole and when i turn the engine on without sparks, the 3 that have gazoline pop right out. The fourth one remains closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 i get 0ohm. I think the issue is elsewhere.

I also tried to reset PID but without success. The car will start when the G28 is not plugged in and it runs perfectly when it is connected but it still has the intermittent misfire issue at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. Also i noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.

I'm not certain what to do, i feel i have pretty much completely ruled out all other possibilities. I'm concerned that i may have missed something. If anyone has any ideas please chime in! TIA!

3. Fuel Pump


The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. It is easy to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing up). They should be infinite Ohms.

4. ECU

spare audi key (3B AAN, ABY and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft to make a decision about timing of the fuel injector, for example. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go wrong, you will receive codes on the diagnostic scanner which can cause the engine to shut down.

The signs of a malfunctioning G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when in gear. If you have any of these issues, it is likely that your sensor is failing and should be replaced. The good thing is that they are quite affordable and readily available particularly when you're looking at the Bosch sensor, which is what we have. You can also choose the GM version of this unit is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous problems in your vehicle. It's an essential component of the transmission of your Audi since it sends information to the ECU regarding how fast or slowly the engine is spinning. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49, via an uncolored wire. The ECU then processes the signal to control the flow of fuel, timig and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Additionally, you can check 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. It should show approximately 1000 ohms resistance between those points. This is the same 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 You may also find good ones in wrecking yards.

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