How to fix: Performance Max conversion goals misconfigured

TL;DR

Performance Max optimizes against whatever conversion actions you mark Primary — when the campaign inherits the account-default mix (Purchase plus Add-to-cart plus Sign-up plus micro-actions all flagged Primary), Smart Bidding chases the cheapest action and starves the revenue action. Override the campaign to a single Primary action that represents real business value, push every other action to Secondary, and expect 10-25% of mis-allocated PMax spend to redirect within 21-30 days [1].

Why it matters

PMax is a fully automated channel: you do not pick keywords, you do not set bids, you do not pick placements. The one lever you fully control is which conversion action Smart Bidding chases. Set that wrong and every downstream signal (audience signal, creative rotation, asset-group weighting, channel mix between Search / YouTube / Display / Gmail) is calibrated to the wrong outcome.

The default behaviour is to inherit the account-level conversion goals. For most audited accounts that means three to six actions are simultaneously marked Primary: Purchase, Add-to-cart, Begin checkout, Sign-up, View key page, sometimes Phone call. Smart Bidding treats every Primary action as fungible for bidding — it does not weight Purchase more than Add-to-cart on its own. Result: the algorithm rapidly learns that Add-to-cart converts five to fifteen times more often than Purchase at a fraction of the CPA, and it floods budget to placements and queries that drive Add-to-cart [2]. Reported ROAS looks fine on the Primary column; the bank account does not.

The fix is conceptually trivial and operationally cheap: tell the campaign to use one Primary action, push the rest to Secondary so they still report but stop driving bidding. This is exactly the surface Google built into the campaign Conversion goals panel [1] — yet it is one of the most under-used surfaces in the platform, because it lives two clicks behind the campaign settings and Google's onboarding does not surface it.

A second failure mode shows up on tROAS campaigns: the campaign is configured for value-based bidding but the Primary action carries no conversion value (no revenue passed to the tag, no static value assigned). The algorithm tries to maximize a value field that is always zero, so it falls back to behaving like Maximize Conversions while reporting nonsense ROAS. This is the fake_roas flag in the Whitead audit and it lives in the same fix path — the override has to land on a Primary action that actually reports value.

This rule owns campaign-level conversion goal override only. Two sibling rules cover adjacent surfaces: [[fix-conversion-goals-alignment]] handles account-level goal categorization (which conversion actions belong to which goal category — Purchase, Lead, Sign-up, etc.) and [[fix-primary-secondary-conversions]] covers the Primary versus Secondary mechanic at action level. Read those if your account-default setup is wrong upstream — fixing the PMax override without first fixing those is a band-aid.

How to fix

1. Open the PMax campaign's conversion goals (Campaign → Settings → Conversion goals). The default state shows "Use account-default goals" with a list of inherited Primary actions.
2. Switch to campaign-level override (toggle "Use a different conversion goal for this campaign"). The UI now lets you re-rank every action between Primary and Secondary for this campaign only — the account defaults stay untouched for other campaigns.
3. Pick exactly one Primary action that represents real business value.
   • eCommerce: Purchase only. Move Add-to-cart, Begin checkout, View product, Add-to-wishlist to Secondary.
   • Lead gen: Submit Lead Form only (or Qualified Lead from CRM via offline conversion import). Move Page view, Newsletter sign-up, Brochure download to Secondary.
   • Local service: Phone call (from ads) or Booking confirmation. Move Direction request, Page view, Click-to-call from website to Secondary.
4. If the campaign uses tROAS or Maximize Conversion Value, confirm the chosen Primary action carries a value. Open Tools → Conversions → click the action → check the Value column. If it shows "Don't use a value", either pipe the real transaction value from the tag (eCom) or set a static value that represents average gross profit per lead (lead gen). Value-based bidding on a zero-value action is broken bidding.
5. Save and accept the learning-phase reset. Smart Bidding re-enters learning for 7-14 days. Cost-per-conversion will spike 10-30% for the first 3-5 days as the algorithm recalibrates; do not panic-revert in week 1. Track cost-per-Primary-action and revenue (not Conversions count) day-by-day from day 7 onward.
6. Verify after 14 days. Pull the campaign segment report: Primary-action conversion volume should hold or climb, Secondary-action volume may drop (expected — bidding no longer chases those), total spend constant or down slightly, revenue / lead-quality up.

Common mistakes

• Marking two "important" actions both Primary to "give the algorithm flexibility". This is the original mistake — Smart Bidding does not balance Primary actions, it sums them. Pick one.
• Overriding the campaign while the account-default setup is still wrong. If Purchase is in the wrong goal category at account level, the PMax override inherits that bad categorization. Fix [[fix-conversion-goals-alignment]] first if applicable.
• Switching to single Primary without checking conversion volume. PMax with one Primary action needs 30 conversions in 30 days at minimum for Smart Bidding to learn. Below that, the override starves the algorithm. Stay on Maximize Conversions until volume builds.
• Putting micro-conversions back as Primary "for learning velocity". A common dark pattern from Google reps on new accounts. Micro-conversions trip the micro_conv_primary flag and re-introduce the original problem.
• Setting tROAS on a campaign where the Primary action has no value. Bidding will collapse to noise. Either assign a static value, pipe real revenue, or downgrade to tCPA.

FAQ

How is this different from account-default conversion goals?
Account defaults apply to every campaign unless overridden. The PMax-level override changes only the one campaign. Use it when one campaign's economics differ from the account average (e.g. a separate PMax pushing newsletter sign-ups versus the main eCom PMax pushing Purchase).

Should I override every PMax campaign or only the underperformers?
Override every PMax campaign where the inherited Primary set contains more than one revenue-divergent action. If your account default is genuinely a single Primary (Purchase only), the override is redundant.

What if I have multiple revenue actions of equal value (e.g. Purchase + Subscription)?
Combine them into one custom conversion goal at account level (see [[fix-conversion-goals-alignment]]) and mark that goal Primary at campaign level. Do not mark both raw actions Primary — Smart Bidding cannot infer their equivalence.

Does the override reset the learning phase?
Yes. Plan for 7-14 days of recalibration and do not change bidding strategy or budget in parallel — one variable at a time.

Does this rule apply to Performance Max for feed-only campaigns (no asset groups)?
Yes. Feed-only PMax (Shopping-style) optimizes on the same conversion goal surface. The override is identical.

Sources

1. Google Ads Help — Use conversion goals to optimize campaign performance. Canonical reference for campaign-specific conversion goals, including primary/secondary override and the "use a different conversion goal for this campaign" toggle.
2. Google Ads Help — Optimization tips for Performance Max campaigns. Google's published optimization guidance for PMax; covers conversion-goal-driven bidding behaviour.
3. Google Ads Help — About Performance Max campaigns. Performance Max campaign-type overview; confirms PMax is conversion-goal-driven end-to-end.