How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches how to replace the G28 Engine Speed Sensor. The sensor is located near the edges of the transmission above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, just above the flywheel ring. This sensor sends a signal via the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is located so that it can start spark and injectors according to the situation.
If this sensor fails the ECU will throw an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).
Testing can be a bit difficult as there are two different connector pins, and they serve different purposes but the most effective method of testing it is to measure the resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is at full operation. Check for signs 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 maximum speed, i noticed a huge reduction in power. It was like the engine had run out of gas. Or my injectors weren't firing. Today, i pulled out the spark plugs, 3 were soaked with gazoline and the fourth was dry. When i crank the engine, there are no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline jump out but the 4th stay closed. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero ohm. audi a5 replacement key 'm assuming the issue is in another place.
I also tried to reset PID without success. The car can start when the G28 is not plugged in and is running fine when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the gauge for oil pressure 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, but i feel i have pretty much completely ruled out all other possibilities. I'm worried that i might have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from 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 so you can easily find one at a wrecking yard or at a parts store. Test them out to do - just put your DMM in resistance mode and take measurements 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 must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines must be aware of the position and speed the crankshaft to determine timing of fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If either of these go wrong, you will receive codes on the diagnostic scanner that can cause the engine to shut down.
A malfunctioning G28 sensor could cause an inaccurate gearbox speed counter and a gearbox which shifts faster than normal, and/or an unfire when in the gear. It is possible that your sensor is failing and needs to be replaced if you experience any of these signs. The good news is they are very affordable and easily accessible, especially if you're looking at the Bosch sensor, which is what we have. Alternatively, the GM version of this part is also a good choice.
5. Tachometer
A damaged engine sensor could cause a number of problems within your vehicle. It is an important part of the transmission in your Audi, as it transmits information to the ECU regarding how fast or slow the engine of the car is spinning. If the sensor fails, it could disrupt the performance of the transmission as well as the other car's components.
The G5 engine sensor is located near the edge of the transmission, just above the flywheel ring. It sends an electrical signal through gray wire to ECU pin T55/49. The ECU then processes this signal to regulate fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. audi a3 replacement key can check for sensor failure by checking continuity from the sensor to the tachometer. Additionally, you can check continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should detect an average resistance of 1000 ohms between these points. This is a typical component 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 might be availble in wrecking yards.