How to Replace replacement audi car key shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via the grey wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear 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 the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer located in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu has to know 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, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of sync with the Intake Camshaft. It could also indicate a chain stretch or a jumpy chain link in the upper timing chain. However, the error code won't appear on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky because there are two pins for the connector and they have different functions 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. Look for signs of coolant or oil in the connector bay if you are experiencing issues with this part.
2. Injectors
Yesterday accelerating full speed from highway paytoll, I experienced massive power loss like the engine is running out of gas or injectors aren't firing anymore. I pulled out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. I put tissue over each injector hole and when I turn the engine on without sparks, the 3 that have gazoline pop right out. The fourth one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. So i assume the problem is elsewhere.
I also tried to reset the PID but with no luck. The car is able to start when the G28 is not plugged in and runs fine when it is connected however it has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even when it is unplugged, shows a temperature of -49c. Also, i noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, i think i've pretty much completely ruled out all other possibilities. But i'm worried that i might have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump of the g28 receives a signal from the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. It is simple to test them to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They should be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the position and speed of the crankshaft to make a decision about timing of the fuel injectors, etc. To accomplish this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will show codes that could lead to the engine shutting down.
Some of the symptoms of a failing G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when in gear. If you experience any of these problems, it is likely that your sensor is going bad and should be replaced. The good news is that they are very cheap and easy to find, especially if you're looking at a Bosch model, like ours. If you prefer, GM's version of this part would be an option.
5. Tachometer
A failing engine sensor could cause a variety of issues in your vehicle. It is an important part of the transmission of your Audi, as it transmits information to the ECU on how fast or slow the car's engine is turning. When this sensor fails, it will affect the performance of the transmission and the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear and sends a signal to the ECU at pin T55/49, via a grey wire. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 and pin T26a/12. You should see approximately 1000 ohms resistance between these two points. This is a typical part across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best ones might be availble in wrecking yards.