2005 XC90 "SIGNAL TOO LOW" FAULT CODES

GILESD · Post by **GILESD** » 29 Jun 2023, 17:42

Hello All,

New member here with a question regarding multiple fault codes on my daughters 2005 Volvo XC90.
7 Fault codes in total all saying “Signal too low”
Fault code are : 616D CAMSHAFT RESET VALVE. EXHAUST
612D CAMSHAFT RESET VALVE. INTAKE
600D TURBOCHARGER CONTROL VALVE
421D CANNISTER PURGE VALVE
432D LEAK DIAGNOSTIC UNIT. VALVE
432D LEAK DIAGNOSTIC UNIT. PREHEATING
432D LEAK DIAGNOSTIC UNIT. PUMP
Anyone have any experience with these same codes popping up and any known fixes? Also the engine has a rough idle and is down on power.
All help much appreciated!

GILES

LOutlaw1 · Post by **LOutlaw1** » 30 Jun 2023, 21:13

Which engine does it have? 2.5T, 2.9T, diesel?

GILESD · Post by **GILESD** » 30 Jun 2023, 22:04

2.5 Turbo with about 160k miles.

Seems like all these sensors are on the same engine wiring harness and so maybe a common ground or 5v /12v reference could be the culprit but harness all looks good. Maybe ECU source of the 5v or sensor ground?
Just wondering if this is a known series of fault codes on these cars to help point me in the right direction.
Thanks for your reply!

Post by **ggleavitt** » 01 Jul 2023, 19:14

You've done some decent investigating. TCV and Evap valve share a common ground branch point inside the harness, 53/309. The LDP valve is more or less a cable connection to ECM, no common ground involved that I can see.

All of them report low, and low for VIDA means open (no current). You have an electrical wiring guide (EWD)? Think you can find one here- https://volvodiag.com/ewd-online-eng/ , courtesy of a guy on Swedespeed. You're looking for 8/28 (TCV), 6/67 (LDP), and 8/18 for the Evap valve. Run through those and see about doing some visual checks, maybe even at the ECM connector level (don't take it off unless you really suspect something). Common grounds are also identified in the EWDs, you'll likely know far more than you wanted when you're done.

Good luck!

GILESD · Post by **GILESD** » 02 Jul 2023, 13:57

Thank you kindly for the informative response and link to the Volvo diagram. That should help greatly in identifying the issues I am having. Ironically I run a company that specializes in race car electronics, data acquisition and wire harness manufacturing (Indcar and LMDh Sportscars) and am well familiar with how most ECU's function and tuning for maximum engine performance but sadly have almost no experience on road car electronics and OBD2 related diagnostics. If all these sensors are getting no current then I am suspecting an ECU reference voltage supply (either 5v or 12v?) or some other kind of ECU internal power supply failure but will hopefully know more once I have checked out the Volvo diagrams.
Thank yo again for your assistance. I will post my findings.