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. This sensor is situated at the edge of transmission over the flywheel gear. It transmits a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. audi a3 key fob replacement thekeylab.co.uk is located on the edge of transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU uses this information to regulate boost and fuel. It also sends an alert 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 also the location of the camshaft so that it can activate the spark and injectors.

If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are out of sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).

Testing is a bit tricky because there are two connector pins, and they serve different purposes however the best way to test it is to measure the resistance between the sensor and the ECU. It should read around 1000 ohms when the sensor is at full operation. Look for evidence of coolant or oil in the connector bay if there are issues with this part.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced a big cut in power as if the engine was running out of gas or injectors aren’t firing anymore. I took out the spark plugs this morning, three were drenched in gasoline and the 4th was dry. I put tissue over each injector hole, and when i start the engine with no sparks, the three that have gazoline pop right out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I got zero ohm. Therefore, i think the issue is somewhere else.

I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However, the intermittent misfire problem continues to occur at higher RPM. The coolant sensor (G62), even when it is unplugged, shows temperatures 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 if i crank up the engine.

I’m not sure what to do, but i think i’ve pretty much ruled out everything else. But i’m worried 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 sender is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or from 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 end of the connector). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed of the crankshaft in order to make a decision about timing of the fuel injector, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner that can lead to engine shutdown.

A damaged G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or a misfire in gear. It is likely that your sensor is failing and needs to be replaced if you encounter any of these signs. They are cheap and easy-to-find, especially in the case of a Bosch unit like ours. Alternately, the GM version of this component is also a good option.

5. Tachometer

A damaged engine sensor could cause a variety of issues in your vehicle. It’s an essential component of the Audi’s transmission as it sends information to the ECU about how 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 sensor is located at the edge of the transmission, over the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU then uses and processes the signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer inside the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see a resistance of approximately 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU So, you may find them in wrecking yards.