The three major credit bureaus have a big say in whether you get approved for a car loan or a mortgage. Now one of them, Experian, is cutting back your access to the information it s feeding to lenders about you.

The issue here is something called the FICO score: the Fair Isaac Corporation (FIC) formula for computing a credit score. Fair Isaac takes data from your credit reports compiled by Experian and the other two major credit bureaus, Equifax (EFX) and TransUnion, and turns that into FICO scores using a proprietary approach.

By law, consumers get free annual access to their credit reports -- but not the credit scores calculated based on the raw data in those reports. Each credit bureau also sells its own credit scores but they use their own models, not FICO's.

FICO is important because it s the dominant formula in use by many lenders. FICO scores range from 300 to 850 (850 being the highest). Lenders may look at one, two or all three of your FICO scores to determine whether they'll give you a loan and at what terms. So consumers need to know their FICO scores from each of the bureaus in order to track down any potential problems and determine what type of loans should be available to them.

Access to all of those scores -- by paying $15.95 apiece at MyFICO.com -- has been available since mid-2003. Yet, after Feb. 13, consumers will no longer have access to their FICO score using Experian data -- even though lenders will still have access to it.

You could believe you have a score of X, but the lender sees Y, says Linda Sherry, a spokeswoman for Consumer Action, a consumer advocate. The consumer has no way of judging how creditworthy they are in the eyes of a lender.

Experian is still selling scores based on its own data -- but it's not the same as the FICO score and not widely used by lenders. Instead, it offers a PLUS score ($15), which uses its own credit-risk formula to generate a three-digit score. It also sells a VantageScore ($5.95), which uses an A-F grading formula developed jointly with Equifax and TransUnion. Few lenders use this score either.

See our article here By taking this step, Experian is limiting what Fair Isaac can sell to consumers potentially sending more consumers straight to Experian to purchase information about themselves.

Here's what consumers need to know:

Q: Is there any way I can get my FICO score that s based on Experian s data?

After Feb. 13, no.

Q: What will I be getting when I go to MyFICO.com?

Fair Isaac says it will continue to sell scores at MyFICO.com based on data from Equifax and TransUnion. Its FICO Credit Complete, which offers FICO scores based on data from each of the three bureaus for $47.85 ($42.84 with annual renewal), will no longer be available, however. Fair Isaac may start offering new packages, but pricing for individual scores won t change, says Craig Watts, a spokesman for Fair Isaac.

Spokesmen for Equifax and TransUnion say neither bureau has plans to follow in Experian s footsteps.

Q: Will this affect my ability to secure new credit?

Possibly. While you won t be able to see the FICO score that uses Experian s data, lenders can still pull it -- and so may make a decision based on information you can t see. Basically, there is no way to be certain that you know which data the lender is basing its decision on. Henson says the scores consumers see, even at MyFICO.com, are educational ones. They are not necessarily by any means the scores lenders are using, she says.

Q: If my scores from the other bureaus are good, why should I care about not being able to see the FICO score from Experian?

While some lenders look at scores from all three bureaus when assessing credit risk, many look at just one. A consumer s score varies -- sometimes significantly -- from bureau to bureau. (When this reporter pulled her scores from the three bureaus Friday, there was a 34-point difference between the highest and lowest.) But in the tightening credit market, even a one-point difference can mean a less favorable interest rate or worse: outright rejection.

Q: How can I make sure my Experian score is as high as possible?

Head to AnnualCreditReport.com and pull a free copy of your Experian report to make sure the bureau calculates your score using accurate information. Your credit report consists of your credit history and is used to help determine your score. There s no guarantee that the score, which is not included on the credit report you receive from AnnualCreditReport.com, will be close to where the other two bureaus peg it. Nevertheless, it s the best you can do without being able to see the results. Beyond that, work to improve your overall credit picture by paying bills on time, limiting balances to below 30% of your credit limits and keeping old accounts in good standing active.

Q: Is the government doing anything to control the practices of the credit-scoring agencies like they are with the credit-card companies?

Although credit scores have come up in Congressional hearings pertaining to credit-card practices and the mortgage crisis, Senate and House committees have yet to schedule anything specific to address credit scoring and the practices of the credit bureaus. Both the House Committee on Financial Services and the House Committee on Energy and Commerce said they had nothing currently in the works.