5 Laws Anyone Working In Audi G28 Should Be Aware Of

How to Replace an Audi G28 Engine Speed Sensor

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 signal to the ECU via the grey wire (T55/49) and then to the tachometer located in the instrument cluster.

1. Engine Speed Sensor

The grey wire is located on the edge of transmission, just above the flywheel ring. The 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 an indication to the G5 tachometer inside the instrument cluster.

The sensor 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 located so that it can trigger spark and injectors accordingly.

If this sensor fails, the ECU will display an error code P00160. G28CarKeys indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumpy chain link in the upper chain. The code won't show 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 has its own functions. The most effective method to test it is to measure the resistance between the ECU and the sensor. It should read around 1000 ohms if the sensor is in full operation. Look for signs of coolant or oil in the connector bay if you are experiencing issues 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 out of gas or the injectors aren't firing any more. I took out the spark plugs this morning and found that 3 were drenched in gasoline and the fourth was unclean. When i crank the engine, there are no sparks, i place a tissue on top of each injector hole and the 3 drenched with gazoline jump out but the 4th one stays shut. I tested the ground connection on ECU pins 14/55,30/55 and 48/55 I get zero ohm. So i assume the problem is somewhere else.

I also tried to reset the PID without success. The car will start when the G28 is unplugged, and it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The temperature sensor for the coolant (G62) shows the wrong temperature of -49c even when i unplug it. I also noticed that the oil gauge in the cockpit shows 2 bars when the actual pressure is 0.

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 suggestions, please share them! TIA!

3. Fuel Pump

The fuel pump in the g28 receives signals from the RPM sensor. The GM-style transmitter is identical to the G4 sender and both work on the 80,100,200, UrS, and RS2 vehicles. You can easily locate an extra in a wrecking shop or parts store. It is simple to test them: simply switch your DMM into resistance mode and test the distance between pins 1 and 2 (with the bump at the connector's end facing upwards). They must be infinite Ohms.

4. ECU

The ECU in our 20vt turbo (3B AAN ABY) engines requires to know the position and speed of the crankshaft to determine timing of fuel injectors, etc. It utilizes a Crank Position Sensor G4 and an Engine Speed Sensor G28 to achieve this. If you are experiencing issues with either of these sensors, the diagnostic scanner will show codes that could cause an engine shutdown.

A damaged G28 sensor could result in an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or a misfire while in the gear. If you are experiencing any of these problems, it is likely your sensor is deteriorating and requires replacement. They're inexpensive and easy to locate especially if they're an Bosch model like ours. Alternately, GM's version this part would be an excellent choice.

5. Tachometer

A failing engine sensor could cause a variety of issues within your vehicle. It's an essential component of the Audi's transmission as it sends information to the ECU about how fast or slow the vehicle's crankshaft is rotating. This sensor can cause the transmission to fail and other components in the car to be affected.

The G5 engine sensor is located near the edge of the transmission, over the flywheel ring. It sends a signal via gray wire to ECU pin T55/49. The ECU uses this signal to regulate the amount of fuel and boost, and also timig. It also relays it to the G5 Tachometer located in the instrument cluster. You can test the sensor for failure by checking 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 approximately 1000 ohms resistance between those points. This is the same across the Audi 80-100-200-RS2 range, from the 1985 MC all the way up to the 1997 UrS AN and the 1995 RS2 DU So, you may find some good ones in wrecking yards.

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Pub: 29 Sep 2024 12:25 UTC
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