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Why Audi G28 Isn't A Topic That People Are Interested In Audi G28
How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is located at the edges of the transmission, just above the flywheel ring. This sensor sends signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.

The sensor is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors in the right way.

If this sensor fails, the ECU will display an error code P00160. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).

It is a little tricky to test since there are different pins on the connector, and each has its own functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. It should read approximately 1000 ohms when it 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, when i was accelerating to the fullest speed from highway paytoll, i experienced massive power loss like the engine is out of gas or injectors are not firing anymore. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was unclean. I put a piece of tissue over each injector hole, and when i turn the engine on without sparks, the 3 with gazoline jump right out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero ohm. I think the issue is elsewhere.

I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. Highly recommended Internet page (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 when the actual pressure is 0.0 when I crank up the engine.

I'm not certain what to do, but i think i've pretty much ruled out everything else. I'm afraid 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 sent from the RPM sensor. The GM-style sensor is the same as 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 in a local parts store. Testing them is easy - 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 left on the black connector's end). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the speed and position of the crankshaft in order to make a decision about fuel injector timing, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner that can cause the engine to shut down.

A failing G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, and/or a misfire while in gear. If you experience any of these issues it is most likely that your sensor is going bad and should be replaced. The good thing is that they are very cheap and easy to find particularly in the case of an Bosch sensor, like ours. You can also choose the GM version of this part is also a good choice.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind a slew of issues with your car. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. If the sensor fails, it can affect the performance of the transmission and the other car's components.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer inside the instrument cluster. You can test 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 on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see a resistance of approximately 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS AN and 1995 RS2 DU You may also find good ones in wrecking yards.

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