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. This sensor is located near the transmission's edge over the flywheel gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of 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 the boost, fuel, and timig. It also sends an indicator to the G5 Tachometer located in the 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 activate spark and injectors in the right way.
If this sensor fails the ECU will show a P00160 code which means the Crank Shaft and Intake Camshaft aren't in sync, 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 tricky because there are two pins for the connector and they perform different functions but the best 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. If you are having problems with this part, check for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine was running out of gas. Or my injectors weren't firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth was dry. When I crank the engine, there are no sparks, I put a piece of tissue on the top of each of the injector holes and the 3 drenched with gazoline jump out but the 4th stays shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got 0ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID but with no luck. The car can start if the G28 is unplugged and is running fine when it is connected, but still has the intermittent misfire issue at higher RPM. car key replacement audi (G62), even when unplugged, still shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.
I'm not sure what to do, as i think i've pretty much eliminated everything else. I'm worried that i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style transmitter 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 wrecking yard or in a local parts store. Testing them is easy - put your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They should be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines requires to know both the speed and position of the crankshaft to make decisions regarding timing of fuel injectors, etc. To do this, it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go badly, you will see codes on the diagnostic scanner that could cause engine shut down.
Some of the signs of a failed G28 sensor are an inaccurate rev counter for the gearbox and gears that shift faster than normal and/or a misfire when you're in gear. If you experience any of these issues it is likely that your sensor is going bad and should be replaced. The good news is they are quite affordable and easy to find, especially in the case of an Bosch model, which is what we have. Alternatively, GM's version of this part would be an option.
5. Tachometer
A failing engine speed sensor could be the cause of many problems in your vehicle. It's an essential component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. If the sensor fails, it will cause problems for the transmission, as well as the rest of the car's components.
The G5 engine sensor is located near the edge of transmission, above the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU utilizes this signal to control fuel and boost, and also to timigrate. It also relays it to the G5 Tachometer inside the instrument cluster. You can check for sensor failure by examining the continuity from 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 [79trace [79]) and between pin T6a/1 as well as pin T26a/12. It should show around 1000 ohms of resistance between those two pins. This is a typical part across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC to the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.