How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. audi a3 replacement key is located on the edge of the transmission, above the flywheel ring gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can start spark and injectors in the right way.
If this sensor fails the ECU will display a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult as there are two different connector pins and they perform different functions but the best way to test it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read approximately 1000 ohms. If you're experiencing issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, as i was accelerating off the highway paytoll at a high speed, i noticed a huge decrease 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 drenched in gasoline and the fourth was unclean. When i crank the engine with no sparks, i place a tissue on the top of each hole in the injector, the 3 drenched with gazoline pop out, but the 4th stay closed. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero ohm. I think the issue is somewhere else.
audi a3 replacement key tried to reset the PID with no success. The car can start if the G28 is not plugged in and is running fine when it is plugged in however it has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, as i think i've pretty much completely ruled out all other possibilities. But i am afraid I may have missed something. If anyone has suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal from the RPM sensor. audi a4 spare key -style sensor is identical to 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 at a parts store. It is simple to test them: simply switch your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will display codes that could lead to an engine shut down.
The signs of a failed G28 sensor are an inaccurate rev counter for the gearbox the gears are shifting faster than normal and/or a misfire when you are in gear. It is probable that your sensor is failing and needs to be replaced if you experience any of these signs. The good news is they are quite affordable and easily accessible, especially in the case of a Bosch unit like ours. You can also choose the GM version of this unit is also a great option.
5. Tachometer
A faulty engine speed sensor could be the reason behind numerous problems in your vehicle. It's an essential component of your Audi's transmission, since it relays information to the ECU about how the car's crankshaft is rotating. This sensor can cause the transmission to fail and other components in the car to be affected.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU is then able to process this signal to control the flow of fuel, timig and boost, and also sends it on to the G5 tachometer inside the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. You can also examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]), and between pin T6a/1 and pin T26a/12. You should see approximately 1000 ohms of resistance between those two pins. This is a standard component across the Audi 80 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.