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 situated on the outside of the transmission over the flywheel gear. It transmits a signal to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission just above the flywheel ring gear the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 via a grey wire. The ECU uses this information to regulate the amount of fuel and boost. It also sends an alert to the G5 Tachometer in instrument cluster.
visit the following website page 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 activate spark and injectors accordingly.
If this sensor fails the ECU will show 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 chain of timing. However the code will not be displayed on its own without additional information from other sensors (G4 and G40).
It is a little tricky to test because there are different connector pins, and each has its own functions. The best method for doing this is by measuring the resistance between the ECU and the sensor. When the sensor is functional, it should read around 1000 ohms. Examine for signs of coolant, or oil in the connector bay if you are experiencing problems with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll i had an abrupt drop in power like the engine is running out of gas or the injectors are not firing at all. This morning i pull out the spark plugs. Three were drenched with gazoline the 4th one was dry. When i crank the engine with no sparks i put tissue on top of each injector hole and the 3 drenched with gazoline pop out, but the 4th one stays shut. I tested the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ i get 0ohm. I think the issue is elsewhere.
I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it works fine when the G28 connected. However the intermittent misfire issue persists at higher RPM. The coolant temperature sensor (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 while the actual pressure is 0.
I'm not sure what to do. I feel like i've pretty much ruled everything else out. But i'm worried that i might have missed something. Let me know if you have any ideas! TIA!
3. Fuel Pump
The fuel pump in the g28 is activated by a signal sent from the RPM sensor. The GM-style transmitter is similar to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily find an extra in a wrecking shop or a parts store. It is easy to test them: simply put your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump on the connector's edge facing upwards). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines must be aware of the speed and position of the crankshaft to determine timing of fuel injectors, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these go badly, you will see codes on the diagnostic scanner that could cause engine shut down.
Some of the signs of a failed G28 sensor include an inaccurate gearbox rev counter, gears shifting quicker than normal, and/or a misfire when you are in gear. It is likely that your sensor is failing and needs to be replaced if you notice any of these signs. They're cheap and easy to find especially in the case of a Bosch unit like ours. Alternately, GM's version this component is an excellent choice.
5. Tachometer
A failing engine sensor could cause a number of problems in your car. It's a vital component of the Audi's transmission since it relays information to the ECU about how fast or slow the vehicle's crankshaft is turning. If this sensor fails, it could disrupt the performance of 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 and sends a signal to the ECU at pin T55/49 through a grey wire. The ECU then uses and processes this signal to control the flow of fuel, timig and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can check for sensor failure by checking continuity from the sensor to the tachometer. You can also 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. It should show approximately 1000 ohms resistance between those two pins. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC up to the 1997 UrS AN and the 1995 RS2 Du So, you may find them in wrecking yards.