How to Replace an Audi G28 Engine Speed Sensor

In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49) and then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is situated on the outside of the transmission, directly above the flywheel ring. The sensor sends signals through the grey wire to pin T55/49. The ECU utilizes 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 as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft 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 not in sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. However, the code won't appear on its own without additional information from other sensors (G4 and G40).

It is a little tricky to test since there are different connector pins, and they all have different functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. It should read about 1000 ohms when it is in full operation. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this part.

2. Injectors

Yesterday accelerating full speed from highway paytoll i had massive power loss like the engine is out of gas or injectors are not firing at all. I pulled out the spark plugs this morning, three were soaked in gasoline, and the fourth was unclean. I put a piece of tissue over each injector hole, and when I turn the engine on without sparks, the three that have gazoline pop right out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. I'm assuming that the issue is in another location.

I also tried to reset the PID without success. The car lost audi key will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue persists at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value that is -49c even after unplugging it. Also, i noticed that the oil pressure gauge in the website cockpit is showing 2 bar when the actual pressure is 0.0 when i rev the engine.

I'm not sure what to do. I believe that I've eliminated everything else. I'm worried that i might spare audi key cost have missed something. Let me know if you have any ideas! TIA!

3. Fuel Pump

The fuel pump of the g28 gets click here a signal from the RPM sensor. The GM-style transmitter 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 salvage yard or in a local parts store. It is simple to test them - just switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines must know the position and speed the crankshaft in order to make a decision about timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these sensors, the diagnostic scanner will show the codes that could trigger an engine shutdown.

A damaged G28 sensor could result in an inaccurate speed counter for your gearbox and a gearbox which shifts more quickly than normal, or a misfire in the gear. If you have any of these issues it is likely your sensor is failing and requires replacement. The good news is that they are very cheap and readily available particularly if you're looking at an Bosch unit which is what ours are. If you prefer, GM's version of this part is an option.

5. Tachometer

A malfunctioning engine speed sensor could be the reason behind many issues in your vehicle. It's an essential component of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the engine is spinning. If the sensor fails, it can disrupt the performance of the transmission as well as the rest of the car's components.

The G5 engine sensor is located at the outskirts of transmission, above the flywheel ring. It sends a signal via a gray wire to the ECU pin T55/49. The ECU then uses and processes the signal to control fuel, timig, and boost, and also sends it on to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. You can audi a1 key also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 and pin T26a/12. There should be an average resistance of 1000 ohms in these areas. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and 1995 RS2 Du You may also find them in wrecking yards.