How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located at the edge of transmission over the flywheel gear. It transmits a signal to the ECU via the grey wire (T55/49) and then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, above the flywheel ring. The sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
replacement car key audi is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors in the right way.
If this sensor fails, the ECU will display an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating the chain is stretched or a jump link on the upper timing chain. The code won't show without the additional information supplied by other sensors (G4 or G40).
It can be a bit difficult to test because there are various connector pins, and they all have 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 it is operating at its maximum. Examine for evidence of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed I noticed a significant drop in power. It was as if the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs. Three were drenched with gazoline the fourth was dry. When i crank the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th one stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. I assume that the problem is somewhere else.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even when it is unplugged, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is 0.
I'm not sure what to do, but i believe that i've ruled out everything else. I'm afraid i may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent by the RPM sensor. The GM-style sender is the same as the G4 and they both work in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. Test them out by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from the left on the black connector's side). They should be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines must know the speed and position of the crankshaft to make decisions regarding fuel injector timing, etc. To do this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes badly, you will see codes on the diagnostic scanner which could cause engine shut down.
The signs of a failed G28 sensor are an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when in gear. It is likely that your sensor is failing and requires to be replaced if you encounter any of these symptoms. They're inexpensive and easy to locate particularly when they're an Bosch sensor like ours. Alternately, the GM version of this unit is also a good option.
5. Tachometer
A damaged engine sensor could cause a variety of issues within your vehicle. It's a crucial component of the transmission in your Audi because it relays information to the ECU regarding how fast or slow the engine of the car is turning. If the sensor fails, it will affect the performance of the transmission as well as the other car's components.
The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU uses this signal to control fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 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 1995 RS2 Du You may also find some good ones in wrecking yards.