How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission just above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU utilizes this information to regulate fuel and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu has to know when the crankshaft reached TDC, and the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain stretching or a jump link on the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
It is a little tricky to test because there are several pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read about 1000 ohms when it is at full operation. If you're having issues with this component, look for evidence 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 out of gas or the injectors are not firing at all. Today, i pulled out the spark plugs, three were soaked with gazoline and the 4th one was dry. I placed a tissue over each injector hole and when i turn the engine on without sparks, the 3 with gazoline jump right out. The 4th one stays shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID without success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value -49c even when i unplug it. I also noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not certain what to do, but i feel i have pretty much ruled out everything else. I'm concerned that i may have missed something. If anyone has any ideas please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. how do i get a replacement key for my audi -style transmitter is identical to the G4 sender and works 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 to do - just put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black end of the connector). They should be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, for example. To accomplish this, it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these go wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown.
The signs of a malfunctioning G28 sensor are an inaccurate gearbox rev counter and gears that shift faster than normal and/or a misfire when you are in gear. It is likely that the sensor is failing and requires to be replaced if you experience any of these signs. The good thing is that they are quite affordable and readily available particularly when you're looking at the Bosch sensor, like ours. Alternatively, GM's version of this component is an excellent choice.
5. Tachometer
A failing engine speed sensor could be a cause for many issues with your vehicle. It's a vital component of your Audi's transmission, since it relays information to the ECU about how fast or slow the vehicle's crankshaft is spinning. If this sensor fails, it can disrupt the performance of the transmission as well as the rest of the car's components.
The G5 engine speed sensor is situated on the edge of the transmission just above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 via a grey wire. The ECU then uses and processes this signal to control fuel, timig, and boost and then transmitting it to the G5 tachometer 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 via pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those points. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU You may also find good ones in wrecking yards.