Paul di Resta topped the second DTM free practice session at Shanghai on Saturday morning, while championship leader Bruno Spengler damaged his car in the closing stages.
Spengler, who leads Mercedes teammate di Resta by three points heading into this weekend's title showdown, clipped the wall with his right-front corner at the beginning of the long final turn with 15 minutes remaining.
The Canadian trailed back to the pits, while the session was red-flagged to allow marshals to clear the track of debris.
Spengler then sat out the rest of the session, and he dropped to 15th as the majority of drivers started to push harder in the final few minutes of practice before the afternoon's qualifying session.
The session restarted in bizarre circumstances, as David Coulthard and Jamie Green both took to the track before the pit exit light had changed from red to green.
Once the session was back under way, Timo Scheider, Miguel Molina and Gary Paffett all took brief turns at the top of the time sheets before di Resta went fastest with six minutes to go.
Several drivers scrapped for second place after that, while di Resta bettered his time again before the end to cement his place at the top.
Green was on course to go fastest as the checkered flag came out, but he was balked heavily in the final corner by Mike Rockenfeller, who was going slowly having started to run out of fuel.
Green then pulled in front of Rockenfeller after the finish line and hit the brakes to show his frustration, while the Audi driver came to a halt after Turn 3 and pulled off the track.
Maro Engel took to the track in his repaired Mercedes just after the halfway stage of the 90-minute session. The German remained out of luck – suffering a punctured radiator on debris from Spengler's crash and only completing eight laps, none of them a proper flying lap.
Pos Driver Car Time Gap
1. Paul di Resta Mercedes 59.390s
2. Jamie Green Mercedes 59.456s + 0.066s
3. Markus Winkelhock Audi 59.459s + 0.069s
4. Oliver Jarvis Audi 59.480s + 0.090s
5. Timo Scheider Audi 59.501s + 0.111s
6. Gary Paffett Mercedes 59.587s + 0.197s
7. Martin Tomczyk Audi 59.606s + 0.216s
8. Mike Rockenfeller Audi 59.634s + 0.244s
9. Miguel Molina Audi 59.710s + 0.320s
10. Mattias Ekstrom Audi 59.771s + 0.381s
11. David Coulthard Mercedes 59.903s + 0.513s
12. Cong Fu Cheng Mercedes 59.919s + 0.529s
13. Ralf Schumacher Mercedes 1m00.201s + 0.811s
14. Susie Stoddart Mercedes 1m00.284s + 0.894s
15. Bruno Spengler Mercedes 1m00.291s + 0.901s
16. Darryl O'Young Audi 1m00.572s + 1.182s
17. Maro Engel Mercedes 1m04.641s + 5.251s
18. Katherine Legge Audi 1m09.402s + 10.012s