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. The sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.

1. Engine Speed Sensor

Located on the edge of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer in the 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 throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync, possibly indicating the chain stretching or a jump link on the upper timing chain. However, the error code won't appear on its own without additional information from other sensors (G4 and G40).

Testing is a bit challenging since there are two connector pins, and they serve different purposes however the best method to test it is to measure the resistance between the sensor and the ECU. It should read approximately 1000 ohms when the sensor is in full operation. If you are having problems with this sensor, look for evidence of oil or coolant in the connector bay.

2. Injectors

Yesterday, as i was accelerating off the highway paytoll at full speed I noticed a massive drop in power. It was as if the engine was running out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the 4th one was dry. When I start the engine, there are no sparks, I put a piece of tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th stays closed. I tried to test the ground connections of ECU pins 14,30, and 48/55. I got zero ohm. So i assume the problem is elsewhere.

I also tried to reset the PID but without success. The car is able to start when the G28 is disconnected and runs fine when it is plugged in however it is more info experiencing intermittent misfires at higher RPM. The coolant sensor (G62) even when unplugged, still shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.

I'm not sure what to do. I think I've all other possibilities out. But i'm worried that I may have missed something. If anyone has suggestions, please let me know! TIA!

3. Fuel Pump

The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style sensor is the same as 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 at a parts store. It is simple 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 must be infinite Ohms.

4. ECU

Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that must be aware of the speed and position of the crankshaft in order to make a decision about fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.

Some of the symptoms of a malfunctioning G28 sensor include an check here inaccurate rev counter in the gearbox the gears are shifting faster than normal and/or misfiring when you're in gear. If you have any of these issues it is likely that your sensor is going bad and requires replacement. The good thing is that they are very affordable and readily available, especially when you're looking at an Bosch unit which is what we have. Alternately, the GM version of this part is also a good choice.

5. Tachometer

A malfunctioning engine sensor can cause a number of problems in your car. It is check here an important part of the transmission in your Audi because it relays information to the ECU regarding how fast or slowly the engine of the car is turning. This sensor could cause the transmission to fail website and other car components to be affected.

The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends signals via an uncolored wire to the ECU pin T55/49. The ECU uses this signal to regulate the flow of fuel and boost and also timig. It also relays website it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be a resistance of approximately 1000 ohms in these areas. This part is common across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 DU So, you may find them in wrecking yards.