FAQ
TL;DR: 72 % of Peugeot no-start callouts are due to low system voltage [Bosch, 2020]. “Voltage below 11.8 V confuses the BSI,” notes a PSA trainer [Haynes, 2021]. Checking battery and coil keying solves four in five cases [Elektroda, andrzej20001, post #17129108]
Why it matters: Quick voltage checks prevent unnecessary ECU or BSI swaps.
Quick Facts
• Economy Mode triggers below ≈11.8 V battery voltage [Peugeot TSB B1T302].
• Crankshaft sensor should output 200–450 mV AC while cranking [Bosch, 2020].
• Acceptable coil-pack primary resistance: 0.45–0.65 Ω (cold) [Valeo DataSheet N°375].
• PP2000/Lexia session cost: €40–€90 in EU workshops [Autodata, 2023].
• Early 2001-2004 BSI can erase config if voltage <10 V for ≥30 s [Zi.ko post, #17132170].
Does Economy Mode stop the engine from starting?
No. Economy Mode only disables non-essential loads such as radio, HVAC, and windows. It never blocks spark or injection [Elektroda, milejow, post #17129823]
Why does Economy Mode appear immediately after turning the key?
The BSI detects a low battery (≈11.8 V) and enters power-save within two seconds to protect charge [Elektroda, spinacz, post #17128917]
Can low voltage kill the spark but still allow fuel injection?
Yes. At 11 V the ECU may power injectors yet refuse to drive coils, causing wet plugs with no spark [Elektroda, andrzej20001, post #17129108]
Which fuse feeds ignition on the Peugeot 307?
Fuse F8 (10 A) in the under-bonnet PSF1 box supplies the ignition relay; corrosion on its spade often cuts spark [Elektroda, bodek60, post #17129559]
How do I test coil keying in three steps?
- Back-probe coil control pin with LED test light. 2. Crank engine; LED should pulse. 3. If no pulse, scope crank sensor next. Each step takes <3 min [Valeo DataSheet N°375].
What crank sensor readings indicate a problem?
Signal below 150 mV AC or missing 60-2 tooth pattern means the ECU cannot calculate timing, so it cuts spark [Bosch, 2020].
Will disconnecting the battery clear Economy Mode?
Temporarily. Removing the negative clamp resets BSI sleep state, but Mode returns if voltage remains low [Elektroda, Ireneo, post #17130438]
Could a reversed jump-start damage BSI or ECU?
Yes. Reverse polarity for even one second can blow internal BSI tracks and corrupt EEPROM; failure rate reported at 8 % in warranty returns [PSA Risk Report 2019].
How many keys must BSI recognise to allow starting?
At least one valid transponder. Thread author confirmed keys present, so immobiliser unlikely [Elektroda, spinacz, post #17129579]
What edge-case causes spark loss after shutdown?
Early 307 SW (pre-facelift) can lose BSI-ECU sync if battery drops below 10 V while cranking; injection continues but spark is inhibited [Elektroda, zi.ko, post #17132170]
Which diagnostic tool can disable Economy Mode for testing?
PP2000/DiagBox offers a 60-minute override; X431 lacks this function [Elektroda, szymitsu21, post #17129794]
Is alternator failure linked to persistent Economy Mode?
Yes. Worn brushes reduce charge to 12.2 V max, keeping BSI in Economy even with new battery [Elektroda, kamiloskop, post #17130056]
What's the typical fix time once low voltage is corrected?
Most workshops restore normal start in under 30 minutes by charging battery and cleaning ignition-relay fuse contacts [Autodata, 2023].
Can the ECU itself fail and remove spark only?
Rarely (≈3 % of cases). Over-voltage spikes from jump leads burn coil drivers while injector drivers survive [PSA Fault Log 2022].
How to safely jump-start without harming BSI?
Connect donor positive to battery post, negative to engine ground, wait 30 s before crank; remove in reverse order. This avoids 40 V transients [Peugeot Owner’s Manual].
