How to Replace G28CarKeys
In this video Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is situated on the outside of the transmission over the flywheel gear. It sends a message to the ECU through a grey wire T55/49, then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
The grey wire is situated at the edges of the transmission, above the flywheel ring. The sensor transmits signals through the grey wire to pin T55/49. The ECU utilizes this information to regulate boost and fuel. It also sends a signal to the G5 tachometer inside the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the position of the camshaft, in order to activate the spark and injectors.
If this sensor fails to function, the ECU will display an error code P00160. This indicates that the Crank Shaft is out of 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. The code won't appear without the additional information provided by other sensors (G4 or G40).
It's a bit tricky to test since there are different pins on the connector and each one has different functions. The best way to do it is to measure the resistance between the ECU and the sensor. It should read approximately 1000 ohms if the sensor is in full operation. Check for signs of coolant, or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, when i was accelerating to the fullest speed from highway paytoll, i experienced an abrupt drop in power as if the engine was running out of gas or injectors aren't firing any more. In the morning, i removed the spark plugs. Three were soaked with gazoline and the fourth one was dry. When I crank the engine with no sparks, I put a piece of tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th one stays closed. I checked the ground connection on ECU pins 14/55, 30/55 and 48/55. I got zero Ohm. I think the issue is elsewhere.
I also tried to reset PID without success. The car can start when the G28 is unplugged and it runs perfectly when it is plugged in however it is experiencing intermittent misfires at higher RPM. The coolant temperature sensor (G62) shows the wrong temp value -49c, even if I unplug it. I also noticed that the gauge for oil pressure in the cockpit shows 2 bar when the actual pressure is 0.0 when I crank up the engine.
I'm not sure what to do. I feel like i've pretty much eliminated everything else. I'm afraid i may have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is the same as the G4 and both are used in the 80, 100, 200, UrS and RS2 cars so you can easily find one at a salvage yard or at a parts store. It is simple to test them: simply put your DMM into resistance mode and determine the distance between pins 1 and 2 (with the bump at the connector end facing up). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY and ADU) engines have an ECU that has to know the position and speed of the crankshaft in order to make decisions about timing of the fuel injectors, etc. To accomplish this, it uses a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you encounter a problem with either of these, the diagnostic scanner will display codes that could cause an engine shutdown.
A malfunctioning G28 sensor can cause an inaccurate speed counter for your gearbox, a gearbox that shifts more quickly than normal, or a misfire in the gear. It is possible that the sensor is failing and requires to be replaced if you experience any of these signs. They're inexpensive and easy to locate especially when they're an Bosch unit like ours. Alternately, the GM version of this part is also a great option.
5. Tachometer
A failing engine speed sensor could be a cause for a slew of issues with your car. It's an essential component of the transmission of your Audi, as it transmits information to the ECU on how fast or slowly the car's engine is spinning. This sensor can cause the transmission to malfunction and other components of the car to be affected.
The G5 engine speed sensor is situated on the outside of the transmission above the flywheel ring gear and transmits a signal to the ECU at pin T55/49 through a grey wire. The ECU utilizes this signal to control fuel and boost, and also to timigrate. It also transmits it to the G5 Tachometer in instrument cluster. You can determine if the sensor is in failure by examining the continuity of 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 and pin T26a/12. You should detect a resistance of approximately 1000 ohms in these areas. This is a common component across the Audi 80, 100, 200, UrS and RS2 range from 1985 MC until the 1997 UrS AAN and 1995 RS2 ADU so good ones might be availble in wrecking yards.