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2005 PT Cruiser OBD2 Codes P0031 P0037 P0714 P0218 P1684: 02 Sensor Upstream/Downstream Issues and Ground Fault Diagnosis

Model: 2005 PT Cruiser Fault Code: P0031 Posted: 2018-08-09 21:42

I recently purchased a used 2005 PT Cruiser and am encountering persistent OBD2 diagnostic trouble codes, including P0031 (Bank 1 Sensor 2), P0037 (Bank 2), P0714 (Transmission Temperature Sensor), P0218 (High Temperature Activator Sensor), and P1684 (Modular Battery Disconnected). The vehicle initially showed codes for both upstream and downstream oxygen sensors, which I replaced. However, after reinstallation, the downstream sensor wiring was found to be damaged due to rubbing against the frame—this issue was resolved by relocating the exhaust pipe and replacing the wire. Despite this, the same OBD2 codes returned, along with a noticeable rough idle under wet conditions. The vehicle runs smoothly during dry weather but becomes unstable when it rains, suggesting an electrical or grounding problem. I suspect a ground fault or poor connection in the sensor circuits, especially since the engine shows low voltage readings on the 02 sensors and the OBD II port intermittently fails to communicate. After clearing codes and replacing components, P0031 and P0037 reappeared. I’ve tried checking fuses, relays, and common ground points such as G102 (left front strut tower), but no consistent resolution has been found. I’m particularly concerned about a potential short or poor grounding in the heater circuits for the 02 sensors—both of which share a common ground point. These circuits are powered by PWM signals and draw approximately 1 amp each, so excessive current could indicate a short to ground. I currently lack access to a multimeter or scan tool with live data capability and am unable to perform proper voltage drop testing between the battery negative terminal and G102. I’ve also noticed that the MIL light remains on during bulb checks (KOE0), which may point to communication issues. The vehicle does not exhibit misfiring, but driveability is noticeably affected in wet conditions. I’m seeking advice from experienced users or mechanics familiar with 2005 PT Cruiser electrical systems—especially regarding grounding, wiring harness integrity, and potential PCM driver faults. Any guidance on diagnosing the root cause of these recurring codes would be greatly appreciated.

Related fault codes
P0031P0037P0218P0714P1684
Comments (10)
Anonymous 2018-08-09 21:55

Please confirm the exact OBD2 error codes you're seeing. BBBind.com provides wiring schematics for common sensor circuits. A digital multimeter (DVOM) is essential to measure voltage and resistance on connectors and wiring paths.

Anonymous 2018-08-09 22:19

Before replacement: P0031 Bank 1 Sensor 2, P0037 Bank 2, P0714 Transmission Temperature Sensor, P0218 High Temp Activator Sensor, and P1684 Modular Battery Disconnected. After replacing the O2 sensors and clearing codes, the same P0031 and P0037 returned.

Anonymous 2018-11-12 13:11

I'm experiencing the exact same issue—SOS! Located in upstate NY. Any help would be much appreciated.

Anonymous 2018-11-12 13:18

This is very strange: the vehicle starts with low voltage on both O2 sensors, then the OBD II port becomes unresponsive. I replaced all related components—ignition switch, brake switch—but codes persist. The cluster still shows errors, and I only get readings via the cluster display. I’ve been chasing this for three months with no garage in upstate NY. Some suggest a coolant temperature sensor issue, but I can’t replace it without knowing where to find it. Others say it might be a faulty PCM—though I’ve heard replacements don’t always fix it. I wish I knew the correct ground point on the PCM since I’m not experienced with automotive electrical systems.

Anonymous 2018-11-12 20:19

What engine type is your vehicle (8th VIN)? Do you have access to a multimeter or an OBD2 scan tool?

Anonymous 2018-11-12 21:27

My OBD II port no longer communicates—codes only appear on the dashboard cluster.

Anonymous 2018-11-12 21:32

This issue seems to stem from communication failure due to a short, ground fault, or dirty throttle body. All fuses and relays are functional. I suspect it might not be the PCM—though some users report fixes after replacement. P0031, P0037, and P0572 appear frequently in 2005 PT Cruisers, yet no definitive fix has been found. Could this be a shared ground issue or wiring fault?

Anonymous 2018-11-13 00:33

Could you please share your engine type (based on 8th VIN)? Does the MIL light stay on after startup during a bulb check (KOE0)?

Anonymous 2018-11-13 00:55

Are you currently seeing only P0031 and P0037? Are there any driveability issues beyond emissions failure?

Anonymous 2018-11-13 08:49

A faulty PCM driver is a possibility. A lab scope would be needed to confirm this. Dealerships can typically diagnose it within an hour using standard flat-rate diagnostics. If there’s a ground fault, you’d expect P0032 and P0038 codes—open grounds elevate circuit voltage. The heater circuits for the 02 sensors are powered by PWM signals and share a common ground at G102 (left front strut tower, black wire). Perform a ground-to-ground voltage drop test between this point and battery negative. Voltage drop should be under 300–400 mV. Check power and ground at DLC pins 16 (power), pin 4 (ground), and pin 5 (ground). These circuits draw about 1 amp—excessive current may indicate a short to ground. Use an ohmmeter or test light. The PCM might be shutting down heater drivers to protect itself. This is less likely since you have codes for two separate O2 sensors with independent power-side PWM wires. If only P0031 and P0037 are present, verify the integrity of the G102 ground connection and ensure proper voltage at DLC pins 16, 4, and 5. A certified ASE shop or dealer should be able to resolve this quickly with correct testing equipment.