KUALA LUMPUR, 6 Feb 2015 (AFP) - The Englishman was in a tie for the halfway lead with Spain's Alejandro Canizares, who shot Friday's lowest round in the field, a bogey-free 65.
Westwood's first-round co-leader, former Major winner Graeme McDowell, tumbled down the board, however, shooting a one-over 73 including three bogeys and a double at the Kuala Lumpur Golf and Country Club.
That left the Northern Irishman six strokes off the pace.
But Westwood, who won last year by seven strokes and carded a 66 on day one, posted yet another steady round on a course that seems a perfect match for his game.
"I played nicely again and probably only hit one poor shot all day, from the middle of the fairway on the fifth hole," said Westwood, who suffered his sole bogey on that hole.
He made amends with six birdies sprinkled across the rest of his card.
"But other than that it was very good and I felt very comfortable. It was great to birdie two of the last three and go from one in front to the three in front," he said.
Canizares, meanwhile, said he had "fun" posting the day's best score.
"I made some great-up-and-downs when I missed a shot, and I'm happy overall. It's a great position to be in and I couldn’t ask for any better," he said.
Austria's Bernd Wiesberger was in sole third after shooting a 66, with England's Paul Waring and Ireland's Peter Lawrie a shot further back.
Thailand's Kiradech Aphibarnrat, who won in 2013, was among those who failed to make the cut, as his second-round 69 was not enough to make up for an 80-stroke debacle the previous day.
Leading second-round scores on Friday in the $3 million Malaysian Open at the Kuala Lumpur Golf and Country Club (par 72):
133 - Lee Westwood (ENG) 66-67, Alejandro Canizares (ESP) 68-65
136 - Bernd Wiesberger (AUT) 70-66
137 - Paul Waring (ENG) 69-68, Peter Lawrie (ENG) 71-66
138 - Richard Bland (ENG) 68-70, Richard T. Lee (CAN) 69-69
139 - Graeme McDowell (NIR) 66-73
140 - Prom Meesawat (THA) 68-72, Alvaro Quiros (ESP) 70-70, Juvic Pagunsan (PHI) 71-69, Andy Sullivan (ENG) 70-70, Gregory Bourdy (FRA) 70-70, Jake Higginbottom (AUS) 69-71