Guthrie had led since midway through the opening day at Lake Malaren and was four shots clear overnight, but a third round of 72 saw him caught at the top of the leaderboard by Spain's Rafael Cabrera-Bello.
Cabrera-Bello carded a 67, the joint lowest round of the day, to finish alongside Guthrie on eight under par, with fellow Spaniard Gonzalo Fernandez-Castano a shot behind after his own 67.
France's Gregory Bourdy also returned a 67 to finish six under, with England's Paul Casey and Scottish pair Craig Lee and Scott Jamieson five under after all three bogeyed the last.
However, Simon Dyson's chances of victory had earlier disappeared when he was disqualified for signing for an incorrect score in the second round, an incident he had "no recollection" of according to tournament officials.
The 35-year-old, six times a winner on the European Tour and joint second at halfway, failed to add a two-shot penalty to his card after an incident on the eighth hole, when he touched the line of his putt after marking his ball.
European chief referee John Paramor said in a statement: "Simon Dyson has been disqualified from the BMW Masters presented by SRE Group under the rules of golf (6-6d). Simon was found to have breached rule 16-1a, which states that a player must not touch his line of putt.
"Television viewers alerted the European Tour to the incident, which took place on the eighth green during the second round, and when the footage was reviewed Simon was seen to touch the line of his second putt after marking and lifting his ball on the green.
"He subsequently failed to add a two-shot penalty to his score when signing his card, and as a result has now been disqualified."
Paramor added on www.europeantour.com: "We reviewed the footage with Simon today and there was no other option but to advise him that he was in breach of rule 16 1-a and that does lead to disqualification because he signed for a wrong score yesterday.
"He was bitterly disappointed, he had no way of explaining why or how he came to do what he did; he had no recollection of it till I showed him and even then he said 'I can't even remember doing it.' It's a very sad thing and unfortunately his event is over."
Dyson's disqualification dealt a huge blow to his chances of making the lucrative Race to Dubai finale.
Only the top 60 on the European Tour money list are eligible for the final event, with Dyson currently ranked 66th. He will now need a good performance in either the WGC-HSBC Champions or Turkish Airlines Open to qualify for the DP World Tour Championship in Dubai.
Dyson is the latest player to have a rules infraction spotted by television viewers, the most famous this year being Tiger Woods taking an incorrect drop during the second round of the Masters.
Woods escaped disqualification on that occasion because rules officials said they had examined his drop on the 15th hole and ruled he had done nothing wrong, but did not speak to Woods before he signed his card.
Guthrie had been three shots clear approaching the end of his round but dropped shots at the 16th and 18th while Cabrera-Bello hit a superb tee shot to three feet on the 17th to set up his fifth birdie in a flawless round.
It took Guthrie almost four minutes to play his third shot on the 18th, the 23-year-old - labelled "the American snail" by on-course commentator Wayne Riley for his lengthy pre-shot routine - choosing to chip from the corner of the green to avoid putting through a collar of rough between him and the hole.
"Overall I was hitting it well and putting well for the most part, but I just let a few shots get away from me towards the end and that's never fun," said Guthrie, who is seeking his first professional win after joining the paid ranks in 2012.
"But I'm tied for the lead going into tomorrow and I'm excited about what the final day holds.
"I'm sure there will be a few nerves in the morning, but that's a good thing. Even though I may look calm on the outside, inside I think all of us get pretty pumped up when you're in that situation. It's a great feeling as a competitor, so bring it on. I'm excited."
Cabrera-Bello, whose last career win came in the Dubai Desert Classic last year, said: "Starting with two birdies was obviously great. It gave me confidence straight away, but just because you get off to a good start doesn't always mean you're going to have a good round. But I stayed patient, and luckily more birdies kept coming.
"It wasn't easy, because even though it was warmer today, it was still quite breezy. The forecast was for the wind to die down, but it only started to die down right at the end of our round."