Flashing arrow...no codes

oldghucker · Post by **oldghucker** » 19 Oct 2017, 13:53

Magic arrow showed up after a engine bay wash (I know, I know). Thought it was a fluke, code reader said P0172 (turbo boost elbow) cleared code. Drove for 3 blocks, flashing arrow/CEL returns. Haven't been able to complete "drive cycles" after clearing initial codes, due to trans in 3rd gear (don't want to cause further damage) and thus, can't pull trans. codes. Any ideas? I'd like to have a little insight before guessing which parts to start replacing (pnp, solenoids, etc). Already did a fluid swap (10 quart-style), fluid was nasty brown, vaguely burnt.
Thanks in advance.
1997 850R sportwagon
+/- 140K

Post by **scot850** » 19 Oct 2017, 15:45

I would (obviously) like to suggest water got into somewhere electrical it shouldn't have.

Check the TCU and ECU in the box behind the RH headlight. If water got in here it could cause a short or a TCU communication issue which may explain the no codes. What are you using to test for the codes by the way? Many non-Volvo specific code readers do not read Volvo transmission codes.

I had an issue with my current project. The only difference was I had a solid orange arrow and an engine checklight. Issue was corroded contacts from the TCU to the connector in the box.

Also check that water has not got into the connector for the ABS module or any of the connectors for the transmission. If water got into any of these, it may have a communication error or cannot read the cars' speed sensors.

If you sprayed the engine compartment I would also suggest you remove the distributor cap and make sure it is dry in there. Water can access that area if not masked off and cause the distributor or the cap to burn out.

Neil

oldghucker · Post by **oldghucker** » 19 Oct 2017, 16:10

scot850 wrote: ↑19 Oct 2017, 15:45 I would (obviously) like to suggest water got into somewhere electrical it shouldn't have.

Check the TCU and ECU in the box behind the RH headlight. If water got in here it could cause a short or a TCU communication issue which may explain the no codes. What are you using to test for the codes by the way? Many non-Volvo specific code readers do not read Volvo transmission codes.

I had an issue with my current project. The only difference was I had a solid orange arrow and an engine checklight. Issue was corroded contacts from the TCU to the connector in the box.

Also check that water has not got into the connector for the ABS module or any of the connectors for the transmission. If water got into any of these, it may have a communication error or cannot read the cars' speed sensors.

If you sprayed the engine compartment I would also suggest you remove the distributor cap and make sure it is dry in there. Water can access that area if not masked off and cause the distributor or the cap to burn out.

Neil

Thanks Neil,
Yeah, I ran through your drying list immediately after I first got the arrow...was POSITIVE it was an electrical short or water intrusion issue, may well have been. Immediately after posting I decided I would try and get a "drive cycle" in, 3rd gear or not. To my surprise, car shifted, reversed, down-shifted perfectly. I reset "pending codes" and arrow/cel is off. I'm not going to start patting myself on the back just yet, but I think I won the "flush/fill lottery"

Post by **scot850** » 19 Oct 2017, 16:34

Although I'm not convinced the flush/fill did the fix, it was clearly well overdue. I think the more likely scenario is that there was moisture in the electrical system somewhere and it may have dried out with you opening them up or just with time and heat.

Whatever the cause, hopefully it stays good going forward and you can take the good karma from doing the overdue trans flush!

Neil.