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How to Replace an Audi G28 Engine Speed Sensor


Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal 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. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends a signal to the G5 Tachometer located in the instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors accordingly.

If this sensor fails, the ECU will display a P00160 error code. audi a5 replacement key indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate an issue with the chain or a jumpy chain link in the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).

Testing can be a bit difficult as there are two different pins for the connector and they have different functions however the best method of testing it is by measuring resistance between the sensor and the ECU. It should read about 1000 ohms when it is operating at its maximum. Check for evidence of coolant or oil in the connector bay if you have issues with this component.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed, i noticed a huge drop in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth was dry. When i crank the engine, there are no sparks, I put a piece of tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I assume that the problem is somewhere else.

I also tried to reset the PID without success. The car can start if the G28 is not plugged in and it runs perfectly when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is 0.

I'm not sure what to do. I believe that I've ruled everything else out. I'm concerned that i may have missed something. If anyone has any ideas please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent by 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 which is why you can easily locate one at a salvage yard or in a local parts store. It is simple to test them by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side 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 know the position and speed of the crankshaft in order to make a decision about fuel injector timing etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.

Some of the signs of a failed G28 sensor include an inaccurate rev counter in the gearbox, gears shifting quicker than normal, and/or a misfire when in gear. It is likely that your sensor is failing and needs to be replaced if you experience any of these signs. The good thing is that they are very affordable and readily available particularly in the case of a Bosch sensor, which is what we have. Alternatively, GM's version of this component is an option.

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, as it transmits information to the ECU regarding how fast or slow the engine of the car is spinning. This sensor can cause the transmission to fail and other components of the car to be affected.

The G5 engine speed sensor is located on the outside of the transmission 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 located in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Additionally, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 and pin T26a/12. There should be the resistance to be around 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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