How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. The sensor is situated near the edges of the transmission just above the flywheel ring gear. It sends a message to the ECU through the grey wire T55/49 and then 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 through an uncolored wire. The ECU then utilizes this information to regulate the boost, fuel, and timig. It also sends an alert to the G5 Tachometer in instrument cluster.
The sensor is used to link the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors accordingly.
If this sensor fails when it fails, the ECU will display a P00160 error message. This means that the Crank Shaft is out of line with the Intake Camshaft. It could also indicate a chain stretch or a jump in the chain link of the upper timing chain. 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 pins for the connector and they serve different purposes however the best method to test it is by measuring resistance between the sensor and the ECU. When the sensor is fully operational, it should read approximately 1000 ohms. Look for signs of coolant or oil in the connector bay if you have problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced massive power loss like the engine is out of gas or injectors aren't firing any more. Today, i pulled out the spark plugs, 3 were drenched with gazoline the fourth one was dry. I put tissue over each injector hole and when I start the engine without sparks, the three that have gazoline pop right out. The 4th one remains closed. I tested the ground connection of ECU pins 14,30 and 48/55. I found 0ohm. So i assume the problem is in another place.
audi keys replacement tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it works fine when the G28 plugged in. However, the intermittent misfire problem still occurs at higher RPM. The coolant sensor (G62), even when unplugged, still shows a temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar but the actual pressure is zero.
I'm not sure what to do. I think I've eliminated everything else. But i am afraid I may have missed something. If anyone has any suggestions, please share them! 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 both function in the 80 100 200, UrS and RS2 cars so you can easily find one at a junkyard or from a parts store. Testing them is easy - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector 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 must know the speed and position of the crankshaft to make decisions about fuel injector timing etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these goes bad you will get codes on the diagnostic scanner that could cause engine shut down.
A damaged G28 sensor could cause an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, and/or an unfire when in the gear. If you are experiencing any of these issues, it is likely that your sensor is deteriorating and requires replacement. The good news is they are very cheap and easy to find particularly if you're looking at an Bosch unit like ours. Alternately, GM's version this part is a good option.
5. Tachometer
A faulty engine speed sensor could be a cause for numerous 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 car's crankshaft is rotating. When this sensor fails, it could cause problems for the transmission, as well as the rest of the car's components.
The G5 engine speed sensor is situated on the outside of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU then processes this signal to control fuel, timig, and boost, and also transmitting it to the G5 tachometer in the instrument cluster. You can check for sensor failure by examining the continuity from the sensor to the tachometer. You can also verify continuity between pin T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79trace [79]), and between pin T6a/1 as well as pin T26a/12. You should see an average resistance of 1000 ohms between these points. This is a common component across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU. Good parts could be found in wrecking yards.