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7 Small Changes You Can Make That'll Make A Huge Difference In Your 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. The sensor is situated near the edges of the transmission, above the flywheel ring gear. It sends a signal to the ECU via a grey wire (T55/49), then to the tachometer located in 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 signals to ECU pin T55/49 via the grey wire. The ECU uses this information to regulate the amount of fuel and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.

The sensor is used to connect with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors according to the situation.

If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).

Testing is a bit challenging because there are two connector pins and they serve different purposes but the most effective method of testing it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is operating at its maximum. If you're experiencing issues with this component, look for evidence of coolant or oil in the connector bay.

2. Injectors

Yesterday, when i was accelerating to the fullest speed from highway paytoll, I experienced an abrupt drop in power like the engine is out of gas or injectors are not firing any more. I pulled out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was dry. When read here start the engine, there are no sparks i put tissue on the top of each of the injector holes, the 3 drenched with gazoline jump out but the 4th stay shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. I assume that the problem is in another location.

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 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also, i noticed that the gauge for oil pressure in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.

I'm not certain what to do, but i think i've pretty much eliminated everything else. I'm concerned that i may have missed something. If anyone has suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a salvage yard or in a local parts store. It is simple to test them - simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to be aware of the position and speed the crankshaft to make decisions regarding fuel injector timing, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner which could cause engine shut down.

Some of the signs of a malfunctioning G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal, and/or a misfire when you are in gear. It is probable that the sensor is failing and requires to be replaced if you experience any of these symptoms. The good news is that they are quite affordable and easy to find particularly when you're looking at a Bosch unit like ours. Alternately, the GM version of this part is also a great option.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems within your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU regarding how fast or slow the engine of the car is turning. This sensor could cause the transmission to malfunction and other components in the car to be affected.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU is then able to process the signal to control the flow of fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should detect an average resistance of 1000 ohms in these areas. This is a typical component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.

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