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 at the edge of transmission, above the flywheel gear. It transmits a signal the ECU via an uncolored wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. audi a1 keys is located on the outside of the transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor is used 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 activate spark and injectors according to the situation.
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 the chain is stretched or a jump link on the upper timing chain. The code will not appear without the additional information provided by other sensors (G4 or G40).
Testing is a bit challenging because there are two pins for the connector and they have different functions but the most effective method of testing it is to measure resistance between the sensor and the ECU. It should read about 1000 ohms if the sensor is operating at its maximum. If you're experiencing issues with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, i experienced massive power loss like the engine is running out of gas or injectors aren't firing at all. In the morning, i removed the spark plugs, three were drenched with gazoline the fourth 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 tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. I'm assuming the issue is in another place.
I also tried to reset the PID but with no luck. The car can start if the G28 is not plugged in and runs fine when it is plugged in however it has intermittent misfire issues at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I think I've eliminated everything else. I'm worried that i might have missed something. Please let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sender 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 salvage yard or in a local parts store. It is simple to test them - just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know both the position and speed of 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 you are experiencing issues with either of these, the diagnostic scanner will show the codes that could trigger an engine shut down.
A damaged G28 sensor could cause an inaccurate speed counter for the gearbox, a gearbox that shifts faster than normal, or a misfire in gear. If you have any of these issues, it is likely your sensor is deteriorating and needs replacing. The good thing is that they are very affordable and easily accessible particularly if you're looking at the Bosch sensor, which is what we have. Alternately, GM's version this part would be a good option.
5. Tachometer
A failing engine sensor could cause a number of problems in your car. It is a crucial part of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. When this sensor fails, it can disrupt the performance of the transmission as well as the other car's components.
The G5 engine speed sensor is located at the edge of the transmission above the flywheel ring gear. It sends a signal directly to the ECU at pin T55/49 through a grey wire. The ECU then uses and processes the signal to control fuel, timig, and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Also, 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 and pin T26a/12. There should be an average resistance of 1000 ohms between these points. This part is common 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 You may also find them in wrecking yards.