What NOT To Do In The Audi G28 Industry
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. This sensor is located at the top of the transmission just above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated on the outside of the transmission, directly above the flywheel ring. This sensor sends 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 a signal to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu has to be aware of when the crankshaft has reached TDC, and where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync and possibly indicating the chain stretching or a jump link on the upper timing chain. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It is a little tricky to test because there are various pins on the connector and each has its own functions. The best way to do it is to measure the resistance between the ECU and the sensor. When the sensor is functional, it should read about 1000 ohms. If you're having issues with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full 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. I took out the spark plugs this morning and found that 3 were soaked in gasoline, and the 4th was dry. When I crank the engine without sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline leap out, however 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.
I also tried to reset the PID but with no luck. The car is able to start if the G28 is unplugged and it runs perfectly when it is plugged in, but still has intermittent misfire issues at higher RPM. The temperature sensor for coolant (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 certain what to do, as i feel i have pretty much completely ruled out all other possibilities. I'm afraid i may have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal from the RPM sensor. you can check here -style sensor is identical to the G4 and they both work in the 80, 100 200, UrS and RS2 cars so you can easily find one at a wrecking yard or in a local parts store. It is simple to test them - put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines are equipped with an ECU that needs to know the speed and position of the crankshaft to make decisions regarding fuel injector timing etc. To accomplish 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 the codes that could trigger an engine shut down.
A damaged G28 sensor could cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or a misfire while in gear. If you are experiencing any of these problems, it is likely your sensor is failing and requires replacement. They're inexpensive and easy to locate especially when they're an Bosch model like ours. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine speed sensor could be a cause for numerous problems in your car. It's an essential component of the Audi's transmission because it communicates to the ECU about how fast or slow the vehicle's crankshaft is spinning. This sensor can cause the transmission to malfunction and other car components to be affected.
The G5 engine sensor is located at the outskirts of the transmission, over the flywheel ring. It transmits signals via an uncolored wire to the ECU pin T55/49. The ECU is then able to process the signal to control fuel, timig and boost and then sends it on to the G5 tachometer inside the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. You should observe around 1000 ohms of resistance between these two points. This part is common across the Audi 80-100-200-RS2 series, starting beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 DU You may also find them in wrecking yards.