How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located at the edge of transmission just above the flywheel gear. It transmits a signal to the ECU via a grey wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the outside of the transmission, just above the flywheel ring. The sensor sends a signal via 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 in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC and also the location of the camshaft in order to activate the spark and injectors.
If this sensor fails when it fails, the ECU will display a P00160 error code. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of the possibility of a chain stretch or jumpy chain link in the upper timing chain. The code won't appear without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult as there are two different connector pins and they serve different purposes however the best method of testing it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms when it is in full operation. If you're having issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at maximum speed I noticed a massive drop in power. It was like the engine had run out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs, three were soaked with gazoline and the fourth one was dry. I put a piece of tissue over each injector hole and when I start the engine with no sparks, the 3 that have gazoline pop right out. The 4th one remains shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got zero Ohm. I think the issue is somewhere else.
I also tried to reset PID but without success. The car will start when the G28 is unplugged, and it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of that is -49c even after unplugging it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do. I feel like i've pretty much all other possibilities out. But i am afraid I may have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent by the RPM sensor. The GM-style transmitter 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 wrecking yard or in a local parts store. It is easy to test them - simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They should be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to make decisions regarding timing of the fuel injector, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you encounter a problem with either of these, the diagnostic scanner will display the codes that could trigger an engine shut down.
A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, or a misfire in the gear. If you experience any of these problems, it is likely your sensor is going bad and should be replaced. They're cheap and easy to find particularly if they're an Bosch model like ours. Alternately, GM's version this component is an option.
5. Tachometer
A faulty engine speed sensor could be a cause for numerous problems in your vehicle. It is a crucial part of the Audi's transmission because it communicates to the ECU about how the car's crankshaft is spinning. This sensor can cause the transmission to malfunction and other components in the car to be affected.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig, and boost as well as sends it on to the G5 Tachometer located in the instrument cluster. The Keylab can test for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. There should be an average resistance of 1000 ohms between these two points. This is a common feature across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS AN and 1995 RS2 DU You may also find good ones in wrecking yards.