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 situated on the outside of the transmission, above the flywheel gear. It transmits a signal to the ECU via an uncolored 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, just 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 the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.

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

If this sensor fails when it fails, the ECU will display an error code P00160. This indicates 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 jumpy chain link in the upper chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).

It can be a bit difficult to test because there are several pins on the connector and each one has different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. If the sensor is functional, it should read about 1000 ohms. Examine for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, when accelerating from highway paytoll at a high speed, i noticed a huge decrease in power. It was like the engine was running out of gas. Or my injectors were not firing. Today, i pulled out the spark plugs, three were drenched in gazoline, the fourth was dry. I put a piece of tissue over each hole in the injector and when i start the engine with no sparks, the three that have gazoline pop right out. The 4th one stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got zero ohm. So i assume the problem is elsewhere.

I also tried to reset PID but without success. The car key replacement audi will start when the G28 is disconnected, but it runs fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures 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 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 of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to 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 in a local parts store. It is easy to test them: simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the position and speed of 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 have a problem with either one of these, the diagnostic scanner will show codes that could lead to an engine shut down.

Some of the symptoms of a failing G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when in gear. It is possible that your sensor is failing and requires to be replaced if you experience any of these signs. The good news is they are very affordable and readily available, especially if you're looking at a Bosch sensor, like ours. Alternatively, GM's version of this part would be an excellent choice.

5. Tachometer

A malfunctioning engine sensor can cause a variety of issues in your vehicle. It's a crucial component of the transmission of your audi q3 key, as it transmits information to the ECU regarding how fast or slow the engine is turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.

The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear and transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU is then able to process the signal to control fuel, timig, and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can test for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]) and audikey between pin T6a/1 as well as pin T26a/12. You should see around 1000 ohms of resistance between those points. This is the same across the audi a4 replacement key 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 Du, so you might find them in wrecking yards.