Case Study: GMC Savana cranks, no start – DTCs P0689, P1682

Sept. 7, 2023

The Savana was towed to the shop because the malfunction indicator light (MIL) was on, and the engine would crank over but not start.

Richard Diegle

Related To: ALLDATA

Vehicle: 2016 GMC Savana 2500, V8-4.8L, automatic transmission/transaxle

Mileage: 242,385

Problem: The Savana was towed to the shop because the malfunction indicator light (MIL) was on, and the engine would crank over but not start.

Case details: The technician connected a scan tool and found these diagnostic trouble codes (DTCs):

P0689 - Engine Controls Ignition Relay Feedback Circuit Low Voltage
P1682 - Ignition 1 Switch Circuit 2

A call to an ALLDATA Tech-Assist consultant got the diagnosis on the right track. The consultant advised checking the power and grounds at the powertrain control module (PCM). If the power and grounds were good, he said to suspect a faulty PCM.

The technician found that the PCM power feeds were weak (under 12V). He inspected the fuse box under the hood and found corrosion on two of the fuse connectors.

Confirmed repair: He cleaned the connectors and fuse box terminals. After that, he cleared the DTCs. The van started up and ran normally. Easy fix!

Reprinted with permission from ALLDATA.

About the Author

Richard Diegle | Senior Automotive Editor for ALLDATA

Rich Diegle has been in the automotive industry since 1978. After graduating from a local community college, he began working at a Nissan dealership as a used car technician. Since then, he’s worked as a Nissan and ASE master automotive technician, shop owner, marketing copywriter, automotive editor, public relations manager, instructor, ALLDATA Tech-Assist team manager, and a senior automotive editor.