Crewskrag3488

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 top of the transmission, above the flywheel ring gear. It sends a message to the ECU through the grey wire T55/49 and then to the tachometer located on the instrument cluster.

1. Engine Speed Sensor

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

The sensor is used to link 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 when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate an issue with the chain or a jumped chain link in the upper timing chain. However the code will not appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit tricky as there are two different connector pins and they perform different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is operating at its maximum. If you're having issues with this component, look for evidence of coolant or oil in the connector bay.





2. Injectors

Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant decrease in power. It was as if the engine had run out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, 3 were drenched with gazoline the fourth was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the ones with gazoline jump right out. The 4th one remains closed. I tested the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. I'm assuming that the issue is elsewhere.

I also tried to reset PID without success. The car is able to start if the G28 is unplugged and runs fine when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when it is unplugged, shows an ice temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 if i crank up the engine.

I don't know what to do. I think I've all other possibilities out. I'm worried that i might have missed something. If anyone has suggestions, please chime in! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or from a parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They should be infinite ohms.

4. audi a1 key replacement of our 20vt turbo (3B AAN ABY) engines requires to be aware of the position and speed the crankshaft to determine timing of fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will display the codes that could trigger an engine shutdown.

A damaged G28 sensor could result in an inaccurate speed counter for your gearbox or a gearbox that shifts faster than normal, and/or an unfire when in the gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these symptoms. The good news is they are very cheap and readily available particularly if you're looking at a Bosch model, which is what we have. Alternatively, the GM version of this component is also a good choice.

5. Tachometer

A failing engine sensor could cause a variety of issues in your vehicle. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the car's crankshaft is rotating. This sensor can cause the transmission to malfunction and other components of the car to be affected.

The G5 engine speed sensor is located at the edge of the transmission above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through an uncolored wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can test the sensor for any failure by checking 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. It should show around 1000 ohms of resistance between those two pins. This is a typical part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.