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Diagnostic code 850

Car ran fine yesterday. Today no start with error code 335. is this related to the pnp switch?








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Diagnostic code 850

No start, but it cranks Ok? The PNP switch would most likely not even allow it to crank. The 3-3-5 code relates to a wiring problem between the ECU and TCM, they sit right next to each other in that box by the right front strut tower. Try pulling the harness off both and cleaning the contact pins with some contact cleaner and soft brush, might just be some corrosion, unless you see some obvious damaged wires around there. This is a strange code.



Here's what the shop manual says.....

Code 3-3-5 (Fault In Wiring Between TCM and ECM)

1) Check status message on Volvo Scan Tool (998-8686). If
status message is PERMANENT FAULT, SIGNAL TOO HIGH or PERMANENT FAULT,
SIGNAL TOO LOW, go to next step. If status message is INTERMITTENT
FAULT, SIGNAL TOO HIGH or INTERMITTENT FAULT, SIGNAL TOO LOW, go to
step 3).

2) If fault is permanent and signal is too high, check wiring
between ECM terminal B26 and Transmission Control Module (TCM)
terminal B15 for a short circuit to voltage. If fault is permanent and
signal is too low, check wiring between ECM terminal B26 and TCM
terminal B15 for a short circuit to ground.

3) If fault is intermittent and signal is too high, check
wiring between ECM terminal B26 and TCM terminal B15 for an
intermittent short circuit to voltage. If fault is intermittent and
signal is too low, check wiring between ECM terminal B26 and TCM
terminal B15 for an intermittent short circuit to ground.



That's all pretty worthless unless you have a Volvo scantool and the wiring diagrams.










Mike
'95 850T








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Diagnostic code 850

335 is listed in the Haynes manual as "Request for malfunction indicator lamp from automatic transmission ECU" which really doesn't tell us anything. I hope someone here can tell you what this means.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.








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Diagnostic code 850

It tells you just what you need to know, that the trans ecu has requested that the fuel injection control unit turn on the MIL. In layman's terms it means to look in the trans ecu for a fault code. In the later model cars it was a code 666 and it meant the same thing.

Mark







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