How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is situated near the transmission's edge over the flywheel gear. It sends a signal to the ECU via a grey wire (T55/49) and then to the tachometer within 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 through the grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an alert to the G5 Tachometer in instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is located so that it can activate spark and injectors accordingly.
If this sensor fails the ECU will show the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain stretching or a jump link on the upper chain of timing. However, the code won't appear on its own, without additional information from other sensors (G4 and G40).
It can be a bit difficult to test as there are different connector pins, and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms when the sensor is in full operation. Look for signs of coolant or oil in the connector bay if there are problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll i had massive power loss as if the engine was running out of gas or injectors aren't firing at all. This morning i pull out the spark plugs. Three were drenched with gazoline the fourth was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the three that have gazoline pop right out. The 4th one stays shut. I inspected the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero Ohm. So i assume the problem is elsewhere.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 connected. However the intermittent misfire issue continues to occur at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. Also, i noticed that the gauge for oil pressure audi spare key 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 pretty much eliminated everything else. However, i'm afraid that i check here might have missed something. If anyone has any suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in 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. You can easily locate an extra in a wrecking shop or parts store. It is simple to test them: simply put your audi spare key DMM into resistance mode and measure 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 are equipped with an ECU that needs to know the speed and position of the crankshaft to make decisions about fuel injector timing etc. It uses a Crank Position Sensor G4 and more info an Engine Speed Sensor G28 to accomplish this. If you are experiencing issues with either one of these, the diagnostic scanner will show codes that could lead to an engine shut down.
A damaged G28 sensor can cause an inaccurate speed counter for the gearbox, a gearbox that shifts more quickly than normal, and/or an unfire when in gear. It is probable that your sensor is failing and requires to be replaced if you experience any of these symptoms. They're inexpensive and easy to locate especially if they're a Bosch model like ours. Alternatively, GM's version of this component is an excellent choice.
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 can cause the transmission to fail and other components in the car to be affected.
The G5 engine sensor is located at the outskirts of the transmission, just above the flywheel ring. It transmits signals via gray wire to ECU pin T55/49. The ECU then processes the signal to control fuel, timig, and boost and then transmitting 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, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show around audi lost key replacement 1000 ohms of resistance between those points. This is a common feature across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 Du, so you might find some good ones in wrecking yards.