How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. This sensor is located near the transmission's edge just above the flywheel gear. It sends a signal to the ECU via an uncolored wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the outside of the transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor is used to link with the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft reached TDC, and the location of the camshaft to trigger 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 line with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumped chain link in the upper chain. However, the error code won't appear on its own, without additional information from other sensors (G4 and G40).
It can be a bit difficult to test since there are several connector pins, and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. If the sensor is operational, it should read about 1000 ohms. Look for evidence of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed, i noticed a huge reduction in power. It was as if the engine had run out of gas. Or, my injectors weren't firing. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the fourth was unclean. When i crank the engine without sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th stays shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero Ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID but with no luck. The car is able to start if the G28 is unplugged and runs fine when it is connected however it has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of that is -49c even after unplugging it. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is zero.
I'm not certain what to do, as i feel i have pretty much ruled out everything else. However, i'm afraid that i might have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal from 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 wrecking yard or in a local parts store. It is easy to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines must know the position and speed the crankshaft to determine fuel injector timing, etc. audi q7 car key replacement utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go badly, you will see codes on the diagnostic scanner which can cause the engine to shut down.
The signs of a failing G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when you're in gear. If you experience any of these issues it is likely your sensor is going bad and should be replaced. The good thing is that they are very affordable and easily accessible, especially if you're looking at an Bosch sensor, like ours. Alternatively, GM's version of this part is an excellent choice.
5. Tachometer
A damaged engine sensor could cause a number of problems within your vehicle. It's a crucial component of the transmission in your Audi because it relays information to the ECU on how fast or slow the engine is turning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It transmits an electrical signal through a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, as well as timig. It also relays it to the G5 Tachometer in 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 on pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect the resistance to be around 1000 ohms between these points. This is a common part across the Audi 80, 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good ones could be available in wrecking yards.