What causes a Gen III LS-swap drive-by-wire system to enter limp mode at wide-open throttle with P1125, P2120, and P2125 despite apparently correct pedal and TPS voltages?
Here is what the documentation says. Each point links to its source; tables and names vary by computer, operating system and tuning software.
- 0411, 1181; LM7, LQ4, LQ9; 1999-2007: The 2003-up Gen III throttle body, TAC module and PCM are not backward compatible with 1999-2002 equipment, so pedal, module and throttle must come from a matched year range. (LS Engine DIY / CarTech)
More in the swap tune checklist, or build a checklist for your swap with the tune checklist tool.
Confidence: medium — sources disagree or are limited; check the sources below.
Further reading
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Sources
- GM Gen III LS PCM/ECM: Electronic Throttle Equipment Guide — LS Engine DIY / CarTech