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, above the flywheel 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

The grey wire is situated on the edge of transmission, above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an alert to the G5 Tachometer in instrument cluster.

The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can activate spark and injectors in the right way.

If this sensor fails, the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).

Testing can be a bit difficult as there are two different connector pins and they have different functions but the best method to test it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is at full operation. If you are having problems with this component, look for signs of coolant or oil in the connector bay.

2. Injectors

Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is running out of gas or the injectors are not firing anymore. This morning i pull out the spark plugs, three were drenched with gazoline the fourth was dry. I put tissue over each injector hole and when i turn the engine on without sparks, the 3 with gazoline jump right out. The fourth one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is elsewhere.

I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the lost audi key engine.

I'm not sure what to do, but i believe that i've ruled out everything else. I'm worried that i might have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal from the RPM sensor. The GM-style sensor is identical to 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 in a local parts store. It is simple to test them: simply put your DMM into resistance mode and determine the audi a1 car key distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.

4. ECU

The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger website an engine shutdown.

Some of the signs of a failed G28 sensor include an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or misfiring when you are in gear. It is likely that the sensor is failing and requires to be replaced if you notice any of these signs. They're inexpensive and easy to locate especially if they're a Bosch model like ours. Alternatively, the GM version of this component is also a good option.

5. Tachometer

A malfunctioning engine speed sensor could be a cause for many issues in your vehicle. It's a vital component of the Audi's transmission as it sends information to the ECU about how the car's crankshaft is turning. This sensor could cause the transmission to fail and other car components to be affected.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends a signal via a gray wire to the ECU pin T55/49. The ECU uses this signal to control the amount of fuel here and boost, and also to timigrate. It also sends it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should detect an average resistance of 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 replacement key for audi a4 MC up to the 1997 UrS AN and the 1995 RS2 DU, so you might find some good ones in wrecking yards.