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How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission above the flywheel ring gear. It transmits a signal to the ECU via an uncolored wire (T55/49), then to the tachometer within the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors according to the situation.
If this sensor fails when it fails, the ECU will display a P00160 error message. This indicates that the Crank Shaft is not in sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jump in the chain link of the upper chain of timing. The code won't appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit tricky as there are two different connector pins and they serve different purposes but the best method of testing it is by measuring resistance between the sensor and the ECU. If the sensor is operational, it should read about 1000 ohms. If you are having problems with this part, check for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll i had an abrupt drop in power like the engine is out of gas or injectors are not firing anymore. I took out the spark plugs this morning, 3 were soaked with gasoline and the 4th was dry. I put a piece of tissue over each injector hole and when i start the engine without sparks, the 3 with gazoline jump out. The 4th one remains shut. I inspected the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero Ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID but without success. audi replacement keys TheKeyLab will start when the G28 is unplugged, and it is running fine with the G28 connected. However, the intermittent misfire problem persists at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is zero.
I'm not sure what to do. I feel like i've pretty much all other possibilities out. I'm worried that i might have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 gets a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and both function in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. It is simple to test them - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines are equipped with an ECU that has to be aware of the speed and position of the crankshaft in order to make a decision about timing of the fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes wrong, you will receive codes on the diagnostic scanner which can lead to engine shutdown.
A malfunctioning G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts faster than normal, and/or a misfire while in gear. If you experience any of these issues it is likely that your sensor is going bad and requires replacement. They're cheap and easy to find, especially in the case of a Bosch model like ours. Alternatively, GM's version of this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a variety of issues within your vehicle. It's a crucial component of the transmission in your Audi because it relays information to the ECU about how fast or slowly the car's engine is turning. When this sensor fails, it will cause problems for the transmission, as well as the rest of the car's components.
The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms resistance between those points. This is a typical part that is found across the Audi 80 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.