Notes

The Most Pervasive Issues With Audi G28
How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

The grey wire is situated at the edges of the transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.

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

If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain stretching or a jump link on the upper timing chain. 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 as there are several pins on the connector and each has its own functions. The best way to do it is by measuring the resistance between the ECU and the sensor. It should read around 1000 ohms when it is at full operation. Check for evidence of coolant or oil in the connector bay if you are experiencing problems with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll i had massive power loss like the engine is out of gas or injectors are not firing at all. This morning i pull out the spark plugs, three were soaked with gazoline and the 4th one was dry. I placed a 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 tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero ohm. So i assume the problem is in another place.

I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures of -49c. Also, i noticed that the oil pressure gauge 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, i feel i have pretty much eliminated everything else. I'm concerned that i may have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from 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 which is why you can easily locate one at a wrecking yard or in a local parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They should be infinite ohms.

4. ECU


The ECU in our 20vt turbo (3B AAN ABY ADU) engines needs to be aware of the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

A damaged G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts more quickly than normal, or a misfire while in gear. It is probable that the sensor is failing and needs to be replaced if you encounter any of these symptoms. They're inexpensive and easy to locate, especially when they're an Bosch sensor like ours. Alternately, the GM version of this component is also a good choice.

5. Tachometer

A faulty engine speed sensor could be a cause for a slew of issues in your car. It's a vital component of the Audi's transmission because it communicates to the ECU about how fast or slow the car's crankshaft is turning. If this sensor fails, it could affect the performance of the transmission and the other car's components.

The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate fuel and boost, and also timig. key for audi relays it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see around 1000 ohms of resistance between those points. This is a standard part across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.

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