Hi, my 2005 C5 2.2HDI with DW12TED4HX motor (VIN VF7**************[VIN obfuscated, can be read by forum staff]) has just come up with SERVICE and ENGINE MAINTENANCE warning lights, and messages "Engine Mgmt System faulty" and "Depollution System faulty". I'm trying to find out the cause, so any help appreciated. We were in the middle of traveling 160km when the warning came up, car maintained its speed so no limp mode fortunately.
When I originally tested the DTC's I got Current: P0487 - exhaust gas recycle throttle control circuit A/Open, P2033 - exhaust gas temperature sensor Circuit high bank 1 sensor 2 ( plus other codes which may be undervoltage caused - P1352, U0055, U0019, U0028 )
I've just installed a new battery to see if the undervoltage codes disappear, but no luck and some additional codes have appeared: P0473 - exhaust pressure sensor A circuit high, P0228 throttle pedal position sensor C circuit high.
I've checked the EGR system
- vacuum checked at solenoid and then bypassed the solenoid and engine cutout at idle
- checked solenoid resistance, 14.5ohm. Don't know what it should be, can't find any detail for Bosch 9-635-704-380 part #
- applied 12V to solenoid, couldn't hear anything, so applied the 12V with engine at idle, engine cut out.
With engine at idle for a couple of minutes the EGR pipe heated up so the system is operating but don't know what triggers this action.
Removing the EGR valve no sign of gunk/blockage ( it's only 1000odd km since I did the head and cleaned everything )
Now I'm checking the exhaust gas temperature sensor. I ran the engine for 20minutes at about 2000rpm, with coolant temperature up to normal levels, and back probed the electrical connector. Not easy to ensure the probe connections, but in 5 minute intervals I got voltage changing from 4.96V, 4.94V ( as the exhaust started heating ) 4.85V, 4.76V, 4.72V and 4.70V ( as exhaust reaching a steady temperature ). Unfortunately the resistance figures from back probing the connector were not consistent. On exhaust cooling and testing the pins on the disconnected connector I got 59.4kohm, then 75kohm 5 minutes late, 110kohm another 10 minutes and 678kohm a further hour later. So the NTC sensor is responding with temperature as expected.
Does anyone have the expected resistance at ambient and various higher temperatures, and the expected voltage to be measured during operation. If you can help I'd really appreciate it.
Thanks.
So the voltage has dropped with exhaust temperature but not by as much as your calcs would suggest. I'll dismantle from the exhaust and try testing as you suggest.