How to Replace an Audi G28 Engine Speed Sensor
Charles the Humble Technician shows how to replace the G28 Engine Speed Sensor. This sensor is located near the edges 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 on the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 via a grey wire. The ECU uses this information to control fuel and boost. It also sends an indication to the G5 tachometer in the instrument cluster.
The sensor serves as a reference point to connect with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will throw a P00160 code which means the Crank Shaft and Intake Camshaft are not in sync and could indicate the chain stretching 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 can be a bit difficult since there are two connector pins, and they serve different purposes but the best method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is functional, it should read around 1000 ohms. If you're experiencing issues with this component, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full speed I noticed a massive reduction in power. audi q5 locked keys in car was as if the engine was running out of gas. Or, my injectors weren't firing. audi q7 keys locked in car pulled out the spark plugs this morning, three were soaked with gasoline and the 4th was dry. I placed a tissue over each injector hole and when I start the engine without sparks, the ones with gazoline jump right out. The 4th one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found 0ohm. I'm assuming the issue is in another place.
I also tried to reset the PID but with no luck. The car will start if the G28 is unplugged and runs fine when it is plugged in, but still has intermittent misfire issues at higher RPM. The coolant sensor (G62), even when unplugged, still shows temperatures of -49c. Also, i noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when i rev the engine.
I don't know what to do. I think I've ruled everything else out. I'm concerned that i may have missed something. Please let me know should you have any suggestions! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style transmitter is identical to the G4 and they both work in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a junkyard or at a parts store. It is easy to test them - just put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing upwards). They must 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 a decision about fuel injector timing etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If you have a problem with either one of these, the diagnostic scanner will display codes that could lead to the engine shutting down.
A malfunctioning G28 sensor could result in an inaccurate gearbox speed counter, a gearbox that shifts more quickly than normal, or a misfire in gear. It is likely that your sensor is failing and requires to be replaced if you notice any of these signs. They are cheap and easy-to-find particularly when they're a Bosch unit like ours. If you prefer, GM's version of this part would be an excellent choice.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for numerous issues in your car. It is a crucial part of your Audi's transmission, since it relays information to the ECU about how fast or slow the car's crankshaft is turning. This sensor can cause the transmission to fail and other car components to be affected.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits a signal via a gray wire to the ECU pin T55/49. The ECU then processes this signal to control the flow of fuel, timig and boost and then sends it on to the G5 Tachometer located in the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. You can also check continuity between pin 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 approximately 1000 ohms of resistance between these two points. This is the same across the Audi 80-100-200-RS2 model, ranging from the 1985 MC up to the 1997 UrS An and 1995 RS2 Du You may also find good ones in wrecking yards.