How To Beat Your Boss On Audi G28
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In this video, Charles the humble mechanic demonstrates how to replace the G28 engine speed sensor. This sensor is located near the edges of the transmission just above the flywheel ring 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
Located on the edge of the transmission above the flywheel ring gear the G28 Engine Speed Sensor sends a signal to ECU pin T55/49 through an uncolored wire. The ECU utilizes this information to regulate the amount of fuel and boost. It also sends an indication to the G5 Tachometer located in the instrument cluster.
The sensor serves as a reference for comparing with the G40 Camshaft Position Sensor. The ecu must know when the crankshaft is TDC and where the camshaft is so it can trigger spark and injectors in the right way.
If this sensor fails, the ECU will display the P00160 error, which means the Crank Shaft and Intake Camshaft are not in sync and possibly indicating chain stretch or a jumped link on the upper chain of timing. The code will not appear without the additional information supplied by other sensors (G4 or G40).
Testing can be a bit difficult because there are two connector pins and they perform different functions but the best method of testing it is to measure the resistance between the sensor and the ECU. When the sensor is functional, it should read approximately 1000 ohms. Examine for signs of coolant, or oil in the connector bay if there are issues with this part.
2. Injectors
Yesterday, when accelerating from highway paytoll at maximum speed I noticed a significant reduction in power. It was as if the engine had run out of gas. Or my injectors were not firing. I took out the spark plugs this morning and found that 3 were soaked with gasoline and the fourth was dry. I placed a tissue over each injector hole, and when i turn the engine on without sparks, the three with gazoline jump out. The 4th one remains closed. I tested the ground connection on ECU pins 14/55, 30/55 and 48/55. i get zero Ohm. I'm assuming the issue is somewhere else.
I also tried to reset the PID with no success. The car can start if the G28 is not plugged in and runs fine when it is plugged in, but still is experiencing intermittent misfires at higher RPM. The temperature sensor for coolant (G62) shows the wrong temperature value of that is -49c even after unplugging it. I also noticed that the oil pressure gauge in the cockpit is showing 2 bar, whereas the actual pressure is 0.0 when I crank up the engine.
I'm not certain what to do, as i think i've pretty much eliminated everything else. I'm afraid i may have missed something. If anyone has suggestions, please share them! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal from the RPM sensor. The GM-style sensor is the same as the G4 and they both work in the 80 100, 200, UrS and RS2 cars which is why you can easily locate one at a salvage yard or in a local parts store. Testing them is easy - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY) engines must be aware of the position and speed of the crankshaft to determine fuel injector timing, etc. It makes use of a Crank Position Sensor G4 and an Engine Speed Sensor G28 to accomplish this. If either of these goes bad you will get codes on the diagnostic scanner which could cause engine shut down.
Some of the symptoms of a failed G28 sensor are an inaccurate rev counter in the gearbox and gears that shift faster than normal and/or a misfire when you're in gear. If you experience any of these problems, it is most likely that your sensor is going bad and requires replacement. The good news is they are very affordable and readily available particularly if you're looking at a Bosch sensor, which is what we have. Alternatively, the GM version of this component is also a great option.
5. Tachometer
A damaged engine sensor could cause a number of problems in your car. It's an essential component of the transmission of your Audi, as it transmits information to the ECU about how fast or slow the engine of the car is spinning. When this sensor fails, it will affect the performance of the transmission as well as the rest of the car's components.
The G5 engine sensor is located at the edge of transmission, above the flywheel ring. It transmits a signal via gray wire to ECU pin T55/49. The ECU is then able to process this signal to control fuel, timig and boost and then transmitting it to the G5 tachometer in the instrument cluster. You can check the sensor for failure by checking continuity between it and the tachometer, between ECU pin T55/49 and the instrument cluster connection to pin T6a/1 (trace [79trace [79]) and between T6a/1 and the instrument cluster pin T26a/12. You should see an average resistance of 1000 ohms between these two points. This part is common across the Audi 80-100-200-RS2 series, starting from the 1985 MC all the way up to the 1997 UrS An and 1995 RS2 DU, so you might find good ones in wrecking yards.