How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician teaches you how to replace the G28 Engine Speed Sensor. This sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU via the grey wire (T55/49) which is then sent to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission just above the flywheel ring gear G28 Engine Speed Sensor sends a signal to ECU pin T55/49 using the grey wire. The ECU then uses this information to control fuel, timig and boost. It also sends an indication to the G5 Tachometer in instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is located so that it can trigger spark and injectors in the right way.
If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft are not in sync and possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
It's a bit tricky to test as there are various connector pins, and they all have different functions. The most effective method to test it is by measuring the resistance between the ECU and the sensor. When the sensor is fully functional, it should read approximately 1000 ohms. Look for evidence of coolant or oil in the connector bay if you are experiencing issues with this component.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge reduction in power. It was like the engine was running out of gas. Or my injectors weren't firing. I took out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. When I crank the engine with no sparks, i place a tissue on top of each injector hole and the 3 that were drenched in gazoline leap out, however the 4th stay closed. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I got 0ohm. Therefore, i think the issue is in another place.
I also tried to reset the PID with no success. The car is able to start if the G28 is unplugged and runs fine when it is connected however it is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (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 is showing 2 bar when the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, as i think i've pretty much ruled out everything else. I'm afraid i may have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The replacement key for audi a3 fuel pump in the g28 can be activated by a signal by the RPM sensor. The GM-style sensor is the same as the G4 and both are used in the 80, 100 200, UrS and RS2 cars so you can easily find one at a junkyard or in a local parts store. Testing them is easy to do - just 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 should be infinite Ohms.
4. ECU
Our 20vt turbo (3B, AAN, ABY and ADU) engines have an ECU that needs to be aware of the speed and position of the crankshaft to make a decision about timing of the fuel injector, for example. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you have a problem with either of these sensors, the diagnostic scanner will display codes that could cause the engine shutting down.
The signs of a malfunctioning G28 sensor include an inaccurate here rev counter in the gearbox and gears that shift faster than normal and/or misfiring when you're in gear. It is likely that the sensor is failing and needs to be replaced if you experience any of these signs. The good thing is that they are very affordable and easily accessible, especially if you're audi car keys looking at the Bosch sensor, which is what ours are. Alternatively, the GM version of this component is also a good choice.
5. Tachometer
A failing engine speed sensor could be a cause for a slew of issues with your vehicle. It is an important part of the transmission in your Audi because it relays information to the ECU regarding how fast or slow the engine of the car is turning. If the sensor fails, it can cause problems for the transmission and the rest of the car's components.
The G5 engine speed sensor is located on the edge of the transmission, above the flywheel ring gear. It sends a signal to the ECU at website pin T55/49 via a grey 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 in the instrument cluster. You can test for sensor failure by examining the continuity of the sensor to the tachometer. Additionally, you can 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 detect the resistance to be around 1000 ohms between these points. This is a standard component across the Audi 80 100 200, UrS and RS2 range from 1985 audi a1 key replacement MC through the 1997 UrS AAN and 1995 RS2 ADU. Good ones could be available in wrecking yards.