Audi G28: The Ugly The Truth About Audi G28
Audi G28: The Ugly The Truth About Audi G28
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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. This sensor is situated near the transmission's edge, above the flywheel gear. It sends a message to the ECU via the grey wire T55/49 and then to the tachometer located on the instrument cluster.
1. Engine Speed Sensor
It is located on the outside of the transmission above the flywheel ring gear, the G28 Engine Speed Sensor sends signals to ECU pin T55/49 via an uncolored wire. The ECU then uses this information to control the flow of fuel, timig and boost. It also sends signals to the G5 tachometer in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu has to know when the crankshaft has reached TDC, and where the camshaft lies so that it can activate the spark and injectors.
If this sensor fails, the ECU will show an error code P00160 which indicates that the Crank Shaft and Intake Camshaft aren't in sync, possibly indicating chain stretch or a jumped link on the upper timing chain. However, the error code won't be displayed on its own without additional information from other sensors (G4 and G40).
Testing can be a bit difficult since there are two connector pins and they have different functions but the most effective way to test it is by measuring resistance between the sensor and the ECU. When the sensor is functional, it should read about 1000 ohms. If you are having problems with this part, check for evidence of coolant or oil 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 had run out of gas. Or, my injectors were not firing. In the morning, i removed the spark plugs. Three were drenched with gazoline the fourth one was dry. I put a piece of tissue over each injector hole and when i start the engine with no sparks, the ones that have gazoline pop right out. The fourth one remains shut. I tried to test the ground connections of ECU pins 14,30 and 48/55. I found zero ohm. I'm assuming that the issue is in another location.
I also tried to reset the PID without success. The car will start when the G28 is disconnected and runs fine when it is plugged in, but still has the intermittent misfire issue at higher RPM. The coolant sensor (G62) even if it is not plugged in, shows temperatures of -49c. I also noticed that the oil pressure gauge in the cockpit shows 2 bar, whereas the actual pressure is 0.0 when i rev the engine.
I'm not certain what to do, i think i've pretty much eliminated everything else. I'm afraid i may have missed something. If anyone has any ideas please let me know! TIA!
3. Fuel Pump
The fuel pump in the g28 can be activated by a signal sent by the RPM sensor. The GM-style transmitter is identical to the here G4 and both are used in the 80, 100, 200, UrS and RS2 cars which is why you can easily locate one at a wrecking yard or at a parts store. It is easy to test them: simply put your DMM into resistance mode and measure the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.
4. ECU
Our 20vt turbo (3B AAN, ABY, and ADU) engines are equipped with an ECU that must know the speed and position of more info the crankshaft to make a decision about timing of the fuel injectors, etc. In order to do this it makes use of a Crank Position Sensor (G4) and an Engine Speed Sensor (G28). If you have a problem with either of these sensors, the diagnostic scanner will display the codes that could trigger the engine shutting down.
A malfunctioning G28 sensor could result in an inaccurate speed counter for your gearbox and a gearbox which shifts faster than normal, and/or an unfire when in the gear. If you have read more any of these problems, it is likely your sensor is deteriorating and needs replacing. The good news is that they are very affordable and easy to find particularly in the case of a Bosch read more sensor, like more info ours. Alternately, the GM version of this unit is also a good choice.
5. Tachometer
A malfunctioning engine speed sensor could be a cause for many issues in your vehicle. It is a crucial part of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is rotating. When this sensor fails, it can affect the performance of the transmission as well as the rest of the car's components.
The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear and sends a signal to the ECU at pin T55/49 via a grey wire. The ECU then processes the signal to control fuel, timig, and boost and then transmitting it to the G5 tachometer inside the instrument cluster. You can test for sensor failure by examining the continuity from the sensor to the tachometer. Also, you can verify 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 a common part 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.