How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission above the flywheel ring gear. It sends a message to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 using an uncolored wire. replacement audi key uses this information to control boost and fuel. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test because there are various pins on the connector and each one has different functions. The best method for doing this is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms when the sensor is at full operation. If you are having problems with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive decrease in power. It was like the engine was running out of gas. Or, my injectors weren't firing. I pulled out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. I put a piece of tissue over each injector hole and when i start the engine without sparks, the three with gazoline jump out. The 4th 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 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 issue continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.
I'm not sure what to do. I think I've all other possibilities out. However, i'm afraid that I may have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter functions similarly to the G4 sender, and both operate on the 80,100,200, UrS, and RS2 vehicles. It is easy to find a spare in a wrecking shop or parts store. It is simple to test them - simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know the position and speed of the crankshaft to make decisions regarding fuel injector timing etc. To do this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either of these sensors, the diagnostic scanner will show codes that could lead to an engine shutdown.
Some of the symptoms of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you are in gear. It is probable that your sensor is failing and requires to be replaced if you encounter any of these signs. They're inexpensive and easy to locate particularly in the case of a Bosch unit like ours. Alternatively, the GM version of this component is also a good choice.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends signals via gray wire to ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also transmits 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 [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see the resistance to be around 1000 ohms between these points. This is a common component across the Audi 80 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.