How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows 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 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 outside of the transmission, directly above the flywheel ring. The sensor transmits a signal via the grey wire to pin T55/49. The ECU uses this information to control boost and fuel. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used to correlate the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies in order to activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error message. This means that the Crank Shaft is not in line with the Intake Camshaft. It could also be a sign of an issue with the chain or a jumpy 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 tricky since 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. It should read approximately 1000 ohms when the sensor is operating at its maximum. Examine for signs of coolant, or oil in the connector bay if you have problems with this part.
2. new audi key , when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was like the engine had run 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 one was dry. When I start the engine without sparks, I put a piece of tissue on the top of each hole in the injector and the 3 drenched with gazoline jump out but the 4th stay closed. I checked the ground connection on ECU pins 14/55,30/55 and 48/55 I get 0ohm. I'm assuming the issue is elsewhere.
I also tried to reset the PID with no success. The car will start when the G28 is disconnected, but it runs fine with the G28 plugged in. However, the intermittent misfire problem continues to occur at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature value of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is zero.
I'm not sure what to do, as i believe that i've completely ruled out all other possibilities. But i'm worried that I might have missed something. Please let me know If you have any suggestions! TIA!
3. Fuel Pump
The fuel pump of the g28 receives signals from the RPM sensor. The GM-style transmitter is the same as the G4 and they both work in the 80 100, 200, UrS and RS2 cars so you can easily find one at a wrecking yard or from a parts store. Test them out to do - just put your DMM in resistance mode and measure between pins 1 (with the bump on the connector's side up) and 2 (2nd from left on the black connector's end). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to know both the speed and position of the crankshaft in order to make a decision about fuel injector timing, etc. In order to do this it utilizes a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will display codes that could lead to an engine shut down.
A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, and/or a misfire in gear. If you are experiencing any of these issues it is likely your sensor is going bad and requires replacement. They're cheap and easy to find especially when they're an Bosch model like ours. If you prefer, GM's version of this component is an excellent choice.
5. Tachometer
A malfunctioning engine sensor can cause a myriad of issues in your vehicle. It's an essential component of the Audi's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is rotating. If this sensor fails, it will affect the performance of the transmission and the other car's components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU is then able to process this signal to control the flow of fuel, timig and boost as well as sends it on 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. Additionally, 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. There should be a resistance of approximately 1000 ohms between these points. This is a common feature across the Audi 80-100-200-RS2 range, beginning with the 1985 MC and up to the 1997 UrS An and 1995 RS2 Du You may also find some good ones in wrecking yards.