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. The sensor is located near the transmission's edge, above the flywheel gear. It transmits a signal to the ECU via a grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 through an uncolored wire. The ECU utilizes this information to control the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
audi keys serves as a reference to correlate with the G40 Camshaft Position Sensor. The ecu must be aware when the crankshaft is TDC and where the camshaft is so it can start spark and injectors accordingly.
If this sensor fails the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. However the code will not appear on its own without additional information from other sensors (G4 and G40).
It is a little tricky to test because there are various connector pins, and they all have different functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. When the sensor is operational, it should read around 1000 ohms. If you're experiencing issues with this component, look 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 significant decrease in power. It was as if the engine was running out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs. Three were soaked with gazoline and the 4th one was dry. When I start the engine with no sparks i put tissue on top of each injector hole and the 3 that were drenched in gazoline pop out, but the 4th stay shut. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. Therefore, i think the issue is elsewhere.
I also tried to reset PID without success. The car will start when the G28 is not plugged in and it runs perfectly when it is connected, but still is experiencing intermittent misfires at higher RPM. The coolant temperature sensor (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the gauge for oil pressure in the cockpit is showing 2 bar when the actual pressure is 0.0 when I crank up the engine.
I'm not certain what to do, as i feel i have pretty much completely ruled out all other possibilities. But i'm worried that i might have missed something. If anyone has any ideas please chime in! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style sender is the same as 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 by putting your DMM in resistance mode and measure between pins 1 (with the bump on the connector's end up) and 2 (2nd from the left on the black connector's end). They should be infinite ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines needs to know the position and speed of the crankshaft to make decisions regarding fuel injector timing, etc. In order to do this it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these, the diagnostic scanner will show codes that could cause an engine shut down.
Some of the signs of a failed G28 sensor include an inaccurate gearbox rev counter the gears are shifting faster than normal and/or a misfire when you are in gear. If you are experiencing any of these problems, it is likely your sensor is failing and should be replaced. The good news is they are quite affordable and easy to find particularly when you're looking at a Bosch model, which is what ours are. Alternately, the GM version of this part is also a great option.
5. Tachometer
A failing engine speed sensor could be the reason behind a slew of problems in your car. 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 turning. If this sensor fails, it could 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 the transmission, over the flywheel ring. It sends signals via a gray wire to the ECU pin T55/49. The ECU utilizes this signal to regulate fuel and boost, and also timig. It also transmits it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by checking 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. You should see around 1000 ohms of resistance between those points. This is a common feature 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 So, you may find some good ones in wrecking yards.