← Back to list

2001 Volvo S40 P0602 and P0700 Trouble Codes: Causes, DIY Fixes, and OBD-II Diagnosis

Model: 2001 Volvo S40 Fault Code: P0602 Posted: 2007-05-16 17:25

My check engine light came on recently in my 2001 Volvo S40, triggering trouble codes P0602 and P0700. I've already inspected all wiring connections and believe the system is otherwise intact. However, I'm unsure about the location or replacement process for the Electronic Control Module (ECM/PCM), and whether it's actually necessary to replace. My main questions are: 1. What specific issues do these codes indicate beyond just 'ECM fault' or 'automatic transmission error'? Are there known common causes in 2001 S40 models? 2. Can I diagnose and fix this myself, or is professional mechanic assistance required? 3. Should I attempt to reset the OBD-II system using my scanner? Will that help identify whether the codes return or if new ones appear? Vehicle details: - Model: 2001 Volvo S40 - Engine: 1.9L inline-four - Transmission: Automatic - Fuel type: 93 octane consistently used - Mileage: 97,000 miles I'm looking for clear, factual guidance on troubleshooting these codes and whether a repair is feasible without going to a dealership.

Related fault codes
P0602P0700
Comments (8)
Anonymous 2007-05-16 18:00

Given the complexity of P0602 (ECM/PCM fault) and P0700 (automatic transmission control error), it's advisable to consult a certified mechanic or dealership, especially since these codes often point to deeper electronic or mechanical issues in older Volvo models.

Anonymous 2007-05-17 15:54

I reset the check engine light and drove over 20 miles. The light hasn’t come back on yet—time will tell if it returns, which would likely prompt a visit to the dealer for further diagnostics.

Anonymous 2007-05-17 16:08

Clearing OBD-II codes without addressing root causes rarely resolves issues and may actually lead to frustration. The car’s computer will often re-detect faults if underlying problems persist.

Anonymous 2007-05-26 20:17

After driving over 300 miles, I received a new code: P0130 (front oxygen sensor bank 1). This suggests a potential front O2 sensor failure. However, my engine also struggles to start—turning over three to four times—which may point to a fuel pressure regulator issue. I'm unsure if these problems are related or whether only one needs repair. Any insights would be appreciated.

Anonymous 2007-05-27 08:26

When was the last time your vehicle had a tune-up and fuel filter replaced? Check fuel pressure and inspect wiring and connections to the O2 sensors. If your scanner can monitor live O2 sensor data, pay close attention to readings—abnormal patterns may indicate deeper issues. Good luck and feel free to share updates.

Anonymous 2007-05-27 18:23

Thanks for the advice! I’ll try monitoring the O2 sensors with my scanner as suggested. I haven’t had a tune-up in over 18 months—this is a good reminder. I’ll keep you posted on how things progress.

Anonymous 2007-05-28 11:06

Always use high-quality, manufacturer-recommended parts—especially spark plugs. Using substandard components can lead to recurring issues and unexpected failures down the road.

Anonymous 2007-08-01 16:05

Hi—I’ve been inactive for a while but wanted to share an update. I replaced my spark plugs with NGK iridium, pre-gapped ones, and had a specialist replace both the fuel pressure regulator and fuel filter. The car now starts smoothly. However, after diagnostics, they found that the check engine light was actually triggered by a broken flex pipe—something I couldn’t hear initially. The O2 sensor issue was a false reading caused by the leak. Fixing the flex pipe costs $150; replacing the entire exhaust system and catalytic converter would be around $600–$650. Does this sound reasonable for a 2001 Volvo S40? This experience may help others avoid misdiagnosing similar issues.