OBD-II Code
P0690
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$25–$900
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$25 (relay) to $900 (TIPM).
P0690 sets when the PCM's sense circuit on the main power relay reads HIGH — the PCM saw voltage on the sense pin when it expected the relay to be off, OR the voltage exceeded the upper operating threshold (typically over 16V) when energized.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0690 sets when the PCM's sense circuit on the main power relay reads HIGH — the PCM saw voltage on the sense pin when it expected the relay to be of…
P0690 sets when the PCM's sense circuit on the main power relay reads HIGH — the PCM saw voltage on the sense pin when it expected the relay to be off, OR the voltage exceeded the upper operating threshold (typically over 16V) when energized. This is the PCM detecting either a stuck-closed relay (contacts welded) or a back-feed from another circuit on the relay's load side.
Cheapest-first ladder
- Pull the relay and bench-check for welded contacts — they should open with no continuity when the coil is de-energized; any continuity across 30-87 with coil off means the contacts have welded, replace the relay.
- Inspect the load-side circuit for back-feed — aftermarket installs (dash cams, lift-pumps, light bars) wired to a constant-12V source can back-feed through a shared splice and confuse the sense circuit; pull aftermarket fuses one at a time and re-test.
- Verify alternator output is in spec (13.5-14.7V running) — an over-volting charging system can push the sense voltage past the upper threshold and look like a sense fault when the actual problem is regulation. Target threshold: 12V sense relay-on (max 16V), 0V sense relay-off. Expensive-misdiagnosis caveat: a stuck-closed main relay can keep the PCM powered after key-off and slowly drain the battery overnight, which gets misdiagnosed as parasitic draw (alarm system, dome light, etc.) when the actual cause is a $25 relay. On Chrysler TIPM-equipped vehicles, a P0690 with a sealed TIPM means the only repair is the full $400-800 module plus programming.
Vehicle-specific patterns2001-2005 Honda Civic/Accord/CR-V K-series throws P0690 less often than P0688/P0689 but when it does, it's almost always a welded main-relay contact…
- 2001-2005Honda Civic/Accord/CR-V K-series throws P0690 less often than P0688/P0689 but when it does, it's almost always a welded main-relay contact set after a high-current event (e.g., a jump-start with reversed cables).
- 2011-2014Chrysler 3.6L Pentastar TIPM internal relays weld closed at a known failure rate; the parasitic-drain symptom is the giveaway.
- 2007-2014GM trucks with under-dash relay blocks throw P0690 from heat-aged contacts that weld during a brief overcurrent.
- 2004-2011Mazda RX-8 throws P0690 from main-relay welding after running with chronically low compression and a dragging starter (the starter pulls high amps and the relay carries some of the inrush).
- 2003-2009Toyota 4Runner/Tacoma 1GR-FE V6 sets P0690 from corroded EFI main-relay sockets that put intermittent high voltage on the sense pin.
Estimated repair$25 (relay) to $900 (TIPM).
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