PaymentPayAction::run

public function run(array $fields)
{
	$checkParamsResult = $this->checkParams($fields);
	if (!$checkParamsResult->isSuccess())
	{
		$this->addErrors($checkParamsResult->getErrors());
		return null;
	}

	$params = [
		'ORDER_ID' => (int)$fields['ORDER_ID'],
		'RETURN_URL' => $fields['RETURN_URL'],
		'ACCESS_CODE' => $fields['ACCESS_CODE']
	];

	return new MainEngineResponseComponent('bitrix:salescenter.payment.pay', 'checkout_form', $params);
}