How to Replace an Audi G28 Engine Speed Sensor
In this video, Charles the Humble Mechanic shows how to replace the G28 engine speed sensor. The sensor is situated near the edges of the transmission, above the flywheel ring gear. It sends a message to the ECU via an uncolored wire T55/49, then to the tachometer in the instrument cluster.
1. Engine Speed Sensor
The grey wire is located on the edge of transmission, above the flywheel ring. This sensor sends an electrical signal through the grey wire to pin T55/49. The ECU then uses this information to control fuel, timig and boost. It also sends signals to the G5 tachometer inside the instrument cluster.
The sensor is used as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and the location of the camshaft so it can trigger spark and injectors according to the situation.
If this sensor fails the ECU will display a P00160 code which means the Crank Shaft and Intake Camshaft are out of sync and could indicate the chain is stretched or a jump link on the upper chain of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).
Testing is a bit challenging since there are two connector pins and they perform different functions however the best way to test it is to measure resistance between the sensor and the ECU. It should read approximately 1000 ohms when it is at full operation. If you are having problems with this sensor, look for signs of oil or coolant in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or, my injectors weren't firing. Today, i pulled out the spark plugs, 3 were drenched with gazoline the fourth one was dry. When I start the engine with no sparks, I put a piece of tissue on the top of each hole in the injector and the 3 that were drenched in gazoline leap out, however the 4th stays closed. I checked the ground connection of ECU pins 14,30 and 48/55. I got 0ohm. Therefore, i think the issue is somewhere else.
I also tried to reset PID without success. The car is able to start when the G28 is disconnected and is running fine when it is connected however it has intermittent misfire issues at higher RPM. The coolant sensor (G62), even if it is not plugged in, shows a temperature of -49c. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar, whereas the actual pressure is 0.0 if i crank up spare audi key cost the engine.
I'm not sure what to do. I feel like i've pretty much all other possibilities out. I'm concerned that i may have missed something. If anyone has any ideas please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 receives a signal from the RPM sensor. The GM-style sensor is identical to the G4 and both function in the 80, 100 200, UrS website and RS2 cars website so you can easily find one at a junkyard or from a parts store. It is easy to test them - simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump on the connector's edge facing up). They must be infinite Ohms.
4. ECU
Our replacement car key audi 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft to make decisions about fuel injector timing etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If either of these sensors go wrong, you will receive codes on the diagnostic scanner that can lead to engine shutdown.
A failing G28 sensor can cause an inaccurate gearbox speed counter or a gearbox that shifts faster than normal, and/or an unfire when in gear. It is likely that the sensor is failing and requires to be replaced if you notice any of these symptoms. They're inexpensive and easy to locate particularly if they're a Bosch unit like ours. Alternately, GM's version this component is an option.
5. Tachometer
A failing engine sensor could cause a number of problems in your car. It is an important part of the transmission of your Audi because it relays information to the ECU on how fast or slow the car's engine is turning. This sensor could cause the transmission to malfunction and other components in the car to be affected.
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 then uses and processes this signal to regulate fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can test the sensor for failure by examining the continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection on pin T6a/1 (trace [79]) as well as between T6a/1, and the instrument cluster pin T26a/12. You should see around 1000 ohms of resistance between those two pins. This is a common part that is found across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS audi a3 replacement key AAN and 1995 RS2 ADU so good parts could be found in wrecking yards.