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Ten Things You Need To Be Educated About Audi G28
How to Replace an Audi G28 Engine Speed Sensor

Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.


1. Engine Speed Sensor

The sensor is located at the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via the grey wire. The ECU then uses this information to control the boost, fuel, and timig. It also sends a signal to the G5 tachometer inside the instrument cluster.

The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to be aware of when the crankshaft has reached TDC, and the position of the camshaft, to trigger the spark and injectors.

If this sensor fails the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating the chain stretching or a jump link on the upper timing chain. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).

Testing can be a bit difficult as there are two different connector pins, and they serve different purposes but the best method of testing it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is at full operation. Examine for signs of coolant or oil in the connector bay if there are issues with this component.

2. Injectors

Yesterday accelerating full speed from highway paytoll, i experienced an abrupt drop in power like the engine is out of gas or injectors are not firing anymore. I pulled out the spark plugs this morning, 3 were drenched in gasoline and the 4th was dry. When i crank the engine, there are no sparks, i place a tissue on the top of each of the injector holes and the 3 that were drenched in gazoline pop out, but the 4th one stays shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I got 0ohm. I assume that the problem is somewhere else.

audi keys tried to reset the PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.

I don't know what to do. I think I've all other possibilities out. However, i'm afraid that i might have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style sender is the same as the G4 and both function in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or from a parts store. Test them out to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft to make a decision about fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either of these, the diagnostic scanner will show codes that could lead to an engine shutdown.

Some of the symptoms of a failed G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal, and/or a misfire when you're in gear. If you are experiencing any of these issues, it is most likely that your sensor is failing and needs replacing. They are cheap and easy-to-find especially if they're an Bosch sensor like ours. Alternately, GM's version this component is a good option.

5. Tachometer

A malfunctioning engine speed sensor could be the cause of numerous issues in your vehicle. It's an essential component of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is rotating. If the sensor fails, it could affect the performance of the transmission, as well as the rest of the car's components.

The G5 engine speed sensor is situated on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also transmits it to the G5 Tachometer in instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du You may also find them in wrecking yards.