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 located at the top of the transmission, above the flywheel ring gear. It transmits a signal the ECU via a grey wire (T55/49) which is then sent to the tachometer within the instrument cluster.
1. Engine Speed Sensor
The grey wire is located at the edges of the transmission, directly above the flywheel ring. The sensor transmits an electrical signal through the grey wire to pin T55/49. The ECU uses this information to regulate the amount of fuel and boost. It also sends a signal to the G5 tachometer in the instrument cluster.
The sensor is used to connect the G40 Camshaft position Sensor. The ecu needs to know when the crankshaft has reached TDC and also the location of the camshaft so that it can activate the spark and injectors.
If this sensor fails to function, the ECU will display a P00160 error code. This indicates that the Crank Shaft is out of alignment with the Intake Camshaft. It could also indicate the possibility of a chain stretch or jumped chain link in the upper chain of timing. However the code will not appear on its own, without additional information from other sensors (G4 and G40).
Testing is a bit challenging because there are two connector pins, and they have different functions but the most effective way to test it is to measure the resistance between the sensor and the ECU. When the sensor is fully operational, it should be reading approximately 1000 ohms. If you are having problems with this component, look for evidence of coolant or oil in the connector bay.
2. Injectors
Yesterday, when accelerating from highway paytoll at full speed, i noticed a huge decrease in power. It was like 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 unclean. When I start the engine without sparks, I put a piece of tissue on the top of each of the injector holes and the 3 drenched with gazoline pop out, but the 4th one stays closed. I inspected the ground connection on ECU pins 14/55/30/55/48/55/14/55/48/ I get zero Ohm. Therefore, i think the issue is elsewhere.
I also tried to reset the PID but without success. The car will start when the G28 is disconnected, but it is running fine with the G28 plugged in. However the intermittent misfire issue persists at higher RPM. The audi a1 key coolant sensor (G62), even when it is unplugged, shows temperatures of -49c. I also noticed that the oil gauge in the cockpit shows 2 bar while the actual pressure is 0.
I'm not certain what to do, i believe that i've eliminated everything else. But i'm worried that i might have missed something. If anyone has any suggestions, please let me know! TIA!
3. Fuel Pump
The fuel pump of the g28 gets a signal from the RPM sensor. The GM-style sender 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 wrecking yard or at a parts store. Testing them is easy to do - just put your DMM in resistance mode and take measurements between pins 1 (with the bump on the connector end up) and 2 (2nd from the left on the black connector's side). They must be infinite Ohms.
4. ECU
The ECU in our 20vt turbo (3B AAN ABY ADU) engines requires to be aware of the speed and position of the crankshaft to make decisions regarding 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, the diagnostic scanner will show codes that could lead to 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, and/or an unfire when in gear. If you have any of these issues it audi advanced key is likely your sensor is going bad and should be replaced. They are cheap and easy-to-find, especially in the case of an Bosch sensor like ours. If you prefer, GM's version of this component is a good option.
5. Tachometer
A failing engine sensor could cause a myriad of issues within your vehicle. here It's a crucial component of the transmission in your Audi since it sends information to the ECU about how fast or slowly the engine is spinning. This sensor could cause the transmission to malfunction and other car components to be affected.
The G5 engine speed sensor is located at the edge of the transmission just above the flywheel ring gear and sends a signal directly to the ECU at pin T55/49 via an uncolored new audi key wire. The ECU then processes this signal to regulate fuel, timig, and boost as well as transmitting it to the G5 tachometer in the instrument cluster. You can check 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 [79trace [79]) and between pin T6a/1 as well as pin T26a/12. You should see an average resistance of 1000 ohms in these areas. This is a common check here part across the Audi 80 100 200, UrS and RS2 range from 1985 MC through the 1997 UrS AAN and 1995 RS2 ADU, so the best parts could be found in wrecking yards.