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. This sensor is located on the edge of the transmission above the flywheel ring gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via an uncolored wire. The ECU uses this information to control boost and fuel. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. audi advanced key must know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors accordingly.
If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper chain. The code won't show without the additional information provided by other sensors (G4 or G40).
audi convenience key 's a bit tricky to test because there are several pins on the connector, and they all have different functions. The best way to do it is by measuring the resistance between the ECU and the sensor. When the sensor is fully operational, it should read about 1000 ohms. Look for signs of coolant or oil in the connector bay if you have issues with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed I noticed a massive drop in power. It was as if the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the 4th was dry. When I start the engine without sparks i put tissue on top of each injector hole, the 3 drenched with gazoline pop out, but the 4th stays shut. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it works fine when the G28 connected. However, the intermittent misfire problem still occurs at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.
I don't know what to do. I feel like i've pretty much all other possibilities out. I'm worried that i might have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style sender is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or at a parts store. It is simple to test them to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end 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 ADU) engines must be aware of the speed and position of the crankshaft to make decisions regarding timing of the fuel injector, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go wrong, you will receive codes on the diagnostic scanner which can cause the engine to shut down.
A malfunctioning G28 sensor could cause an inaccurate speed counter for your gearbox or a gearbox that shifts more quickly than normal, or an unfire when in the gear. If you experience any of these problems, it is likely your sensor is failing and should be replaced. The good news is that they are very cheap and easily accessible, especially if you're looking at a Bosch unit which is what we have. Alternatively, GM's version of this part is a good option.
5. Tachometer
A failing engine sensor could cause a number of problems within your vehicle. It is a crucial part of your Audi's transmission, as it sends information to the ECU about how the car's crankshaft is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 and 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 model, ranging from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU, so you might find good ones in wrecking yards.