How to Replace an Audi G28 Engine Speed Sensor
In this video Charles the Humble Mechanic demonstrates how to replace the G28 engine speed sensor. The sensor is located on the outside of the transmission just above the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU utilizes this information to regulate boost and fuel. It also sends an indicator to the G5 Tachometer within the instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can start spark and injectors accordingly.
If this sensor fails to function, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate an issue with the chain or a jump in the chain link of the upper chain of timing. The code won't show without the additional information supplied by other sensors (G4 or G40).
It's a bit tricky to test since there are several pins on the connector and each has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is operational, it should read about 1000 ohms. If you're experiencing issues with this part, check for signs of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at a high speed I noticed a massive decrease in power. It was as if the engine had run out of gas. Or my injectors were not firing. In the morning, i removed the spark plugs, three were drenched in gazoline, the 4th one was dry. I placed a tissue over each injector hole, and when I turn the engine on without sparks, the ones that have gazoline pop right out. The 4th one remains shut. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 i get zero Ohm. Therefore, i think the issue is somewhere else.
I also tried to reset PID without success. The car will start when the G28 is unplugged, and it runs fine with the G28 connected. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars but the actual pressure is 0.
I'm not certain what to do, but i feel i have pretty much ruled out everything else. I'm concerned that i may have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 and both are used in the 80 100 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or at a parts store. how do i get a replacement key for my audi is simple to test them: simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to know 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 achieve this. If either of these go bad you will get codes on the diagnostic scanner which can lead to engine shutdown.
A damaged G28 sensor could result in an inaccurate speed counter for the gearbox and a gearbox which shifts more quickly than normal, or a misfire in the gear. If you experience any of these issues, it is likely that your sensor is deteriorating and needs replacing. The good thing is that they are quite affordable and easy to find, especially in the case of the Bosch model, like ours. Alternatively, the GM version of this component is also a great option.
5. Tachometer
A failing engine sensor could cause a variety of issues in your car. It is an important part of the transmission of your Audi because it relays information to the ECU regarding how fast or slow the engine of the car is turning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located at the outside of the transmission, above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 via an uncolored wire. The ECU then processes this signal to control the flow of fuel, timig and boost, and also sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for any failure by checking the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those two pins. This is a standard part that is found across the Audi 80, 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.