How to Replace an audi a1 key G28 Engine Speed Sensor
Charles the Humble Technician shows you how to replace the G28 Engine Speed Sensor. The sensor is located at the top of the transmission above the flywheel ring gear. It sends a message to the ECU through an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The sensor is located at 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 a grey wire. The ECU utilizes this information to control boost and fuel. 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 has to know when the crankshaft has reached TDC and also the position of the camshaft, so that it can activate the spark and injectors.
If this sensor fails, the ECU will display the P00160 error, 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).
Testing is a bit challenging because there are two connector pins, and they serve different purposes but the best way to test it is to measure resistance between the sensor and the ECU. If the sensor is operational, it should read around 1000 ohms. If you are having problems with this sensor, look for evidence of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at maximum speed I noticed a massive reduction in power. It was as if the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I put a piece of tissue over each injector hole, and when I turn the engine on without sparks, the three with gazoline jump right out. The 4th one stays shut. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I get zero Ohm. So i assume the problem is somewhere else.
I also tried to reset the PID with no success. The car can start if the G28 is not plugged in and runs fine when it is connected, but still has the intermittent misfire issue at higher RPM. The temperature sensor for coolant (G62) shows the wrong temp value that is -49c even after unplugging it. Also, i noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when i rev the engine.
I'm not sure what to do, but i think i've pretty much ruled out everything else. However, i'm afraid that I may have missed something. If anyone has any suggestions, please chime in! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both are used in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard 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
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that needs to know the speed and position of the crankshaft in order to make decisions regarding timing of the fuel injector, for example. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these sensors go bad you will get codes on the diagnostic scanner that could cause engine shut down.
A malfunctioning G28 sensor could cause an inaccurate speed counter for the gearbox or a gearbox that shifts more quickly than normal, or an unfire when in the gear. It is probable that the sensor is failing and needs to be replaced if you experience any of these signs. They're inexpensive and easy to locate especially in the case of an Bosch unit like ours. Alternately, GM's version this part is an option.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for numerous issues with your car. It is a crucial part of the audi a3 spare key's transmission as it sends information to the ECU about how fast or slow the car's crankshaft is turning. When 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 at the edge of the transmission just above the flywheel ring gear. It sends a signal to the ECU at pin T55/49 via a grey wire. The ECU utilizes this signal to control fuel and boost, as well as timig. It also transmits it to the G5 Tachometer in instrument cluster. You can test the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should detect an average resistance of 1000 ohms in these areas. This is a common part across the audi key car audi a1 key case (www.northwestu.edu) 80 100 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU. Good ones might be availble in wrecking yards.