Notes On Intermittents

If DTC B337 shows as "History", without any other DTCs, then check the ignition feed, ground, and data circuits for intermittent faults. If other data codes are stored, see DTC EO47, B333-B337: SERIAL DATA CIRCUIT MULTIPLE INTERMITTENT CODES .

NOTE: The following numbered steps refer to circled numbers on diagnostic chart. See Fig 1 . For circuit identification, see Figure .

First check that the code is not intermittent.
This step determines if the fault is due to the power or ground circuits or the data line.
This step checks if the data line fault is in CKT 800 or at the programmer.
This step checks for Ignition-3 to the programmer.

Fig 1: DTC B337: Loss Of HVAC Programmer Data Flow Chart

Courtesy of GENERAL MOTORS CORP.