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. The sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal the ECU via the grey wire (T55/49) and then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, just above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate fuel and boost. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors accordingly.
If this sensor fails, the ECU will display a P00160 error code. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of 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 can be a bit difficult since there are two pins for the connector and they have different functions but the best way to test it is by measuring resistance between the sensor and the ECU. It should read approximately 1000 ohms if the sensor is in full operation. If you're experiencing issues with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, i experienced a big cut in power like the engine is out of gas or the injectors aren't firing any more. This morning i pull out the spark plugs, three were drenched in gazoline, the fourth one was dry. When I start the engine without sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline leap out, however the 4th stays closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. So i assume 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 problem continues to occur at higher RPM. The coolant sensor (G62) even when it is unplugged, shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar when the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do, but i believe that i've ruled out everything else. I'm concerned that 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 by the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate a spare in a wrecking shop or a parts store. It is easy to test them - simply switch your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that needs to be aware of the speed and position of the crankshaft to make a decision about fuel injector timing etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go bad you will get codes on the diagnostic scanner that can cause the engine to shut down.
Some of the signs of a failing G28 sensor include an inaccurate gearbox rev counter and gears that shift faster than normal, and/or a misfire when in gear. It is likely that the sensor is failing and requires to be replaced if you experience any of these signs. They're cheap and easy to find particularly if they're a Bosch unit like ours. If you prefer, GM's version of this part would be an excellent choice.
5. Tachometer
A failing engine speed sensor could be a cause for many problems in your car. It's an essential component of the transmission in your Audi, as it transmits information to the ECU on how fast or slow the engine of the car is spinning. If the sensor fails, it could disrupt the performance of the transmission and the rest of the car's components.
how do i get a replacement key for my audi is situated on the outside of the transmission above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49, via an uncolored wire. The ECU then uses and processes the signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 Tachometer located in the instrument cluster. You can determine if the sensor is in failure by examining the continuity of 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 [79trace [79]), and between pin T6a/1 as well as pin T26a/12. There should be a resistance of approximately 1000 ohms between these two points. This is the same across the Audi 80-100-200-RS2 series, starting 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.