10 Tips For Getting The Most Value From Audi G28
How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the edge of transmission over the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission, above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 using an uncolored wire. The ECU then utilizes this information to regulate fuel, timig and boost. It also sends an indicator to the G5 Tachometer in instrument cluster.
The sensor is used as a reference to correlate with 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 according to the situation.
If this sensor fails, the ECU will display a P00160 error message. This means that the Crank Shaft is out of sync with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumped chain link in the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging as there are two different connector pins and they perform different functions but the most effective method to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should read about 1000 ohms. If you are having problems with this part, check for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating at full speed from the highway paytoll, I experienced massive power loss as if the engine was running out of gas or the injectors are not firing at all. This morning i pull out the spark plugs, three were soaked with gazoline and the fourth one was dry. I put a piece of tissue over each injector hole and when i turn the engine on without sparks, the ones with gazoline jump right out. The 4th one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I found 0ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID but with no luck. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However, the intermittent misfire problem persists at higher RPM. The coolant sensor (G62), even when it is unplugged, shows an ice temperature of -49c. I also noticed that the oil gauge in the cockpit shows 2 bars while the actual pressure is zero.
I'm not certain what to do, but i believe that i've ruled out everything else. I'm concerned that i may have missed something. Let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is similar to the G4 sender and works on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or a parts store. Testing them is easy by putting your DMM in resistance mode and measure the resistance between pins 1 (with the bump on the connector's end up) and 2 (2nd from the 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 needs to know the position and speed of the crankshaft to make decisions regarding timing of the fuel injectors, etc. It uses a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If spare audi key of these go bad you will get codes on the diagnostic scanner that can lead to engine shutdown.
A failing G28 sensor could cause an inaccurate speed counter for the gearbox and a gearbox which shifts faster than normal, and/or an unfire when in the gear. If you are experiencing any of these issues it is likely your sensor is failing and needs replacing. The good thing is that they are quite affordable and easily accessible, especially if you're looking at an Bosch model, which is what we have. If you prefer, GM's version of this part is a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues in your vehicle. It is an important part of the transmission in your Audi because it relays information to the ECU regarding how fast or slowly the car's engine is turning. If this sensor fails, it will cause problems for the transmission as well as the other car's components.
The G5 engine speed sensor is located on the edge of the transmission just above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 through an uncolored wire. The ECU utilizes this signal to regulate the amount of fuel and boost, and also timig. It also relays it to the G5 Tachometer inside the instrument cluster. You can determine if the sensor is in failure by examining the continuity of the sensor to the tachometer. Also, you can examine the continuity between pins T55/49 of the ECU and pin T6a/1 of the instrument cluster (trace [79]) and between pin T6a/1 as well as pin T26a/12. You should observe around 1000 ohms of resistance between those 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. Good parts could be found in wrecking yards.