How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. This sensor is situated at the edge of transmission over the flywheel gear. It transmits a signal to the ECU via an uncolored wire T55/49, then to the tachometer 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 an electrical signal to ECU pin T55/49 via a grey wire. The ECU utilizes this information to control boost and fuel. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft reached TDC, and where the camshaft lies to trigger the spark and injectors.
If this sensor fails the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft aren't in sync and could indicate the chain is stretched or a jump link on the upper chain of timing. However, the code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit tricky because there are two connector pins, and they serve different purposes but the most effective method to test it is to measure resistance between the sensor and the ECU. When the sensor is operational, it should be reading approximately 1000 ohms. Check for signs of coolant or oil in the connector bay if there are problems with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge drop 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, three were soaked with gasoline and the 4th was dry. I put tissue over each injector hole, and when i start the engine without sparks, the three with gazoline jump right out. The 4th one stays shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I got zero ohm. I assume that the problem is in another location.
I also tried to reset the PID but with no luck. The car will start when the G28 is not plugged in and it runs perfectly when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of -49c even when i unplug it. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I feel like i've pretty much ruled everything else out. However, i'm afraid that I might have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style transmitter is the same as the G4 and both function in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or in a local parts store. It is simple to test them - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector 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 needs to know the speed and position of the crankshaft in order to make decisions regarding fuel injector timing etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you are experiencing issues with either one of these, the diagnostic scanner will display codes that could lead to an engine shutdown.
The signs of a failing G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal and/or misfiring when you are in gear. If you experience any of these problems, it is most likely that your sensor is deteriorating and needs replacing. The good news is they are quite affordable and easily accessible, especially when you're looking at a Bosch unit which is what we have. Alternately, the GM version of this unit is also a great option.
5. Tachometer
A damaged engine sensor could cause a number of problems within your vehicle. It is a crucial part of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is rotating. If the sensor fails, it will cause problems for the transmission, as well as the rest of the car's components.
Link Home Page is located on the edge of the transmission above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 through an uncolored wire. The ECU then uses and processes this signal to control fuel, timig, and boost as well as sends it on to the G5 Tachometer located in the instrument cluster. You can check the sensor for failure by examining the continuity between it and the tachometer, between the ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. There should be the resistance to be around 1000 ohms between these two points. This is a common part across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.