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2006 Pontiac G6 P0700 and P1818: Transmission Slipping in 1st & 2nd Gear - PCM or Transmission Replacement?

Model: pontiac g6 Fault Code: P0700 Posted: 2014-07-04 09:19

My 2006 Pontiac G6 has been displaying multiple transmission-related codes, none of which were initially the P0700. After resolving all other codes, the vehicle continues to experience transmission slipping specifically in first and second gear. Recently, both P0700 (Transmission Control Module Range/Performance Problem) and P1818 (Transmission Fluid Pressure Switch Circuit Malfunction) have reappeared. I've already replaced the transmission fluid pressure switch (TFP), and the temperature gauge is functioning normally. I'm now considering two options: replacing the Powertrain Control Module (PCM) for approximately $100, or installing a new transmission (a more expensive option) with potential additional costs if the issue turns out to be related to the PCM. Based on my research, I’m leaning toward the PCM replacement. I'm seeking expert advice—what would you do in this situation? Specifically: Is P1818 typically caused by a faulty TFP switch or a software issue in the PCM? Given that the TFP has already been replaced and the temperature gauge works properly, could this be a false positive or a calibration issue? I’d appreciate detailed input from experienced users who have faced similar issues with 2006 Pontiac G6s.

Related fault codes
P0700P1818
Comments (6)
Anonymous 2014-07-04 10:18

Before making any decisions, please provide all current diagnostic trouble codes (DTCs), describe the full drivability symptoms, and share your vehicle's history—including any modifications or aftermarket parts. A complete picture is essential for accurate diagnosis.

Anonymous 2014-07-04 12:58

The P1818 code has returned after replacing the TFP switch. The transmission slips only in first and second gear. The temperature gauge remains functional, which suggests the TFP sensor itself may not be the root cause.

Anonymous 2014-07-04 14:12

No other symptoms—only slipping in 1st and 2nd gears. Did you replace the transmission fluid pressure (TFP) switch? Is the transmission actually slipping, or is there a noticeable RPM flare between first and second gear? A subtle but known issue: RPM flares can mimic transmission slippage. When P1818 sets, the PCM commands full line pressure—this is a key clue. A pressure check should be performed immediately. To diagnose properly, use a professional scan tool to monitor TFP switch position and actual shifter position: - Park/Neutral: Signal = HI / HI - Reverse: Signal = HI / LOW - Drive: Signal = LOW / HI - Invalid: Signal = LOW / LOW TFP voltage readings: Low = 0V, High = Battery Voltage. After clearing the DTCs, compare TFP signal position with actual shifter position. If they don’t match, the issue likely lies in sensor circuitry or wiring. If the TFP is functioning correctly and no mismatch exists, a false P1818 may have been triggered. In such cases, an updated PCM calibration (reflash) can resolve it—this is available for 2006 Pontiac G6 models.

Anonymous 2014-07-04 16:54

Thanks—I'll try these diagnostic steps using a scan tool and monitor the TFP signal during driving.

Anonymous 2014-07-04 17:05

Can I get a PCM calibration update at an auto parts store? Or is this only available through a dealership or professional service?

Anonymous 2014-07-05 12:56

The calibration update requires a reflash, not just a device. I asked about other symptoms because they could influence the root cause. Clarifying whether you're experiencing actual slippage or an RPM flare is critical—this distinction helps determine if it's a mechanical issue or a sensor/PCM software problem. A professional-grade scan tool is required to perform accurate diagnostics and interpret TFP signal data properly.