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How to Replace an Audi G28 Engine Speed Sensor

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

1. Engine Speed Sensor

Located on the edge of the transmission, above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through a grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.

If this sensor fails to function, the ECU will display a P00160 error code. This means that the Crank Shaft is not in alignment with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jump in the chain link of the upper timing chain. audi key replacement will not appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult since there are two pins for the connector and they serve different purposes but the best method of testing it is to measure the resistance between the sensor and the ECU. If the sensor is operational, it should be reading about 1000 ohms. If you're having issues with this part, check for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. Today, i pulled out the spark plugs. Three were soaked with gazoline and the fourth one was dry. I put tissue over each injector hole, and when I start the engine without sparks, the 3 with gazoline jump right out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get 0ohm. I'm assuming the issue is in another place.

I also tried to reset the PID but with no luck. The car will start if the G28 is unplugged and is running fine when it is connected, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit is showing 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 completely ruled out all other possibilities. However, i'm afraid that I might have missed something. If anyone has any suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style sender is identical to the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or at a parts store. It is simple to test them to do - just put your DMM in resistance mode and take measurements 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) engines requires to be aware of the position and speed the crankshaft in order to make a decision about fuel injector timing, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these goes wrong, you will receive codes on the diagnostic scanner that can lead to engine shutdown.

Some of the signs of a failing G28 sensor include an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you are in gear. If you have any of these issues it is most likely that your sensor is going bad and requires replacement. They're cheap and easy to find, especially if they're a Bosch unit like ours. Alternately, the GM version of this part is also a good choice.

5. Tachometer

A faulty engine speed sensor could be a cause for a slew of problems 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 rotating. When this sensor fails, it can affect the performance of the transmission and the rest of the car's components.

The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through an uncolored wire. The ECU is then able to process this signal to regulate the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see approximately 1000 ohms of resistance between those two pins. This is a standard component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.