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 located at the top of the transmission just above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49), then to the tachometer located in the instrument cluster.
1. Engine Speed Sensor
Located on the edge of the transmission just above the flywheel ring gear, the G28 Engine Speed Sensor sends an electrical signal to ECU pin T55/49 through an uncolored wire. The ECU uses this information to regulate fuel and boost. It also sends an alert to the G5 Tachometer within the instrument cluster.
The sensor is used to correlate with the G40 Camshaft position Sensor. The ecu must know when the crankshaft has reached TDC, and the location of the camshaft to trigger the spark and injectors.
If this sensor fails, the ECU will throw the P00160 error, which means the Crank Shaft and Intake Camshaft are out of sync, possibly indicating the chain is stretched or a jump link on the upper chain of timing. The code won't appear without the additional information supplied by other sensors (G4 or G40).
Testing is a bit challenging since there are two connector pins, and they serve different purposes however the best method of testing it is to measure the resistance between the sensor and the ECU. If the sensor is functional, it should read approximately 1000 ohms. If you are having problems with this part, check for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, while accelerating from the highway paytoll at full speed, i noticed a huge reduction in power. It was as if the engine was running out of gas. Or, my injectors were not firing. I pulled out the spark plugs this morning, three were drenched in gasoline and the fourth was dry. I put tissue over each injector hole and when I start the engine without sparks, the three with gazoline jump out. The fourth one remains shut. I checked the ground connection of ECU pins 14,30, and 48/55. I found zero ohm. I'm assuming the issue is in another place.
I also tried to reset the PID but without success. The car will start when the G28 is unplugged, and it runs fine with the G28 plugged in. However the intermittent misfire issue still occurs at higher RPM. The coolant sensor (G62) even when unplugged, still shows an ice temperature of -49c. Also i noticed that the oil pressure gauge in the cockpit shows 2 bar while the actual pressure is 0.0 if i crank up the engine.
I'm not sure what to do. I believe that I've ruled everything else out. But i'm worried that I may have missed something. If anyone has any ideas please share them! TIA!
3. Fuel Pump
The fuel pump on the g28 is activated by a signal sent 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 from a parts store. It is simple to test them - put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector's end up) and 2 (2nd from left on the black connector's end). They should be infinite Ohms.
4. ECU
The ECU of our 20vt turbo (3B AAN ABY ADU) engines requires to know the speed and position of the crankshaft in order to make a decision about timing of the fuel injector, etc. To accomplish this, it uses 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 codes that could cause an engine shut down.
A failing G28 sensor can cause an inaccurate speed counter for the gearbox or a gearbox that shifts faster than normal, or an unfire when in gear. If you have any of these problems, it is likely your sensor is going bad and needs replacing. The good news is that they are quite affordable and easily accessible particularly in the case of an Bosch unit which is what we have. You can also choose the GM version of this component is also a good choice.
5. Tachometer
A damaged engine sensor could cause a myriad of issues within your vehicle. It's an essential component of your Audi's transmission, because it communicates to the ECU about how fast or slow the vehicle's crankshaft is turning. This sensor can cause the transmission to malfunction and other components in the car to be affected.
The G5 engine speed sensor is located at the edge of the transmission, above the flywheel ring gear. It transmits a signal to the ECU at pin T55/49 via an uncolored wire. The ECU utilizes this signal to regulate fuel and boost, as well as timig. It also relays it to the G5 Tachometer inside the instrument cluster. audi key replacement can test the sensor for failure by checking continuity between it and the tachometer. You can also check continuity between ECU pin T55/49 and the instrument cluster connection via pin T6a/1 (trace [79]) and between pin T6a/1 and the instrument cluster pin T26a/12. It should show approximately 1000 ohms of resistance between those two pins. This is the same across the Audi 80-100-200-RS2 series, starting from the 1985 MC up to the 1997 UrS An and 1995 RS2 DU So, you may find some good ones in wrecking yards.