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 near the edges of the transmission above the flywheel ring gear. It sends a message 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 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 needs to be aware of when the crankshaft has reached TDC, and where the camshaft lies 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 and possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).

Testing is a bit challenging because there are two pins for the connector and they serve different purposes but the best method of testing it is by measuring resistance between the sensor and the ECU. When the sensor is fully functional, it should read approximately 1000 ohms. If you're experiencing issues with this part, check for evidence of coolant or oil in the connector bay.

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 the injectors aren't firing anymore. I pulled out the spark plugs this morning, 3 were soaked in gasoline, and the fourth was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the 3 with gazoline jump out. The fourth one remains closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero ohm. I assume that the problem is somewhere else.

I also tried to reset PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. Also i noticed that the oil pressure gauge in the cockpit shows audi a4 spare key 2 bar when the actual pressure is 0.0 if i crank up the engine.

I'm not sure what to do. audi key replacement near me I feel like i've pretty much ruled everything else out. I'm concerned that i may have missed something. Let me know If you have any suggestions! TIA!

3. Fuel Pump

The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is easy to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's audi replacement keys edge facing upwards). They must be infinite Ohms.

4. ECU

Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to be aware of the speed and position of the crankshaft to make a decision about timing of the fuel injectors, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go badly, you will see codes on the diagnostic scanner which can lead to engine shutdown.

A malfunctioning G28 sensor can more info cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, or an unfire when in the gear. If you are experiencing any of these issues, it is likely your sensor is going bad and needs replacing. They're inexpensive and easy to locate particularly if they're a Bosch unit like ours. Alternately, GM's version this part is an excellent choice.

5. Tachometer

A malfunctioning engine sensor can cause a variety of issues in your car. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. If this sensor fails, it can cause problems for the transmission as well as the rest of the car's components.

The G5 engine speed sensor is located at the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the 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. You should observe approximately 1000 ohms resistance between those points. This is a standard part that is found across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the audi lost key 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.