2003 GMC Savana 3500 P0135 and P0152 O2 Sensor Issues Causing Engine Stalling in Cold Weather
The check engine light on my 2003 GMC Savana 3500 1 Ton Van with a 6.0L V8 engine first appeared in April, approximately 10 months ago. I had it scanned regularly and was consistently told the issue was related to oxygen (O2) sensors — generally considered minor — except for one shop that recommended replacing them to pass emissions tests. Since my vehicle is registered in a non-emissions-controlled area, I declined those repairs. In December, the truck began exhibiting idle problems when cold. The engine would stall briefly and then rev itself up, with the voltmeter showing erratic fluctuations. When driving without warming up, the check engine light would flash. I took it to the dealer, who recommended replacing O2 sensors, spark plugs, and ignition wires, followed by a fuel flush. After clearing several misfire and O2 sensor codes, they only reported P0135 and P0152 returning post-clearance. The manager stated that 'replacing the O2 sensors would likely be sufficient.' I authorized this repair. However, after driving for a few days while waiting for delivery of the parts, the symptoms persisted. When I returned to the dealer, I asked if any new codes had appeared — they did not keep records. I also asked whether the check engine light was cleared, and the manager confirmed it was not on record and suggested a 'tune-up' due to a misfire on cylinder 6. At $350 for spark plugs and wires plus 2.5 hours of labor, I sought a second opinion. A different shop initially quoted $12.50 per plug and 1.8 hours of labor, but after questioning the necessity, they performed a diagnostic and found P0135, P0152, P0154, P0155, and P0300. They asked if I had already replaced the O2 sensors and advised me to return to the dealer for repairs — which I am now hesitant to do due to concerns about being charged additional 'tune-up' fees. I have several questions: Do I have legal or technical recourse against the dealer? What should I expect from them if they insist on a tune-up? Given that independent shops charge significantly more than online retailers (e.g., $50 spark plug kits and $3–$4 per plug), is it worth paying premium prices for parts and labor? Additional details: - The van has 15,000 miles since the alternator failed and was replaced in November. - Total mileage: approximately 215,000 miles. - Purchased in September 2012 at 147,000 miles. - Since then, I’ve replaced the battery, rear brakes, front left hub, and all four tires. - After the check engine light began flashing, a USB charging adapter failed once to charge my phone — though no further testing has been done. - The driver’s side headlight dims and brightens intermittently. I am seeking clarity on whether P0135 and P0152 are indicative of faulty O2 sensors or deeper engine issues, and what steps I should take to resolve this effectively without being overcharged.
1) Always use the correct spark plug type — such as AC Delco — as specified in the owner's manual (part number listed there). 2) If there is no compelling reason to avoid replacement, all ignition wires should be replaced. 3) A qualified technician with a diagnostic scanner and live data monitoring is strongly recommended. Currently, you have four O2 sensor codes — three of which relate to the same sensor (B2S1), and one (B1S1). Additionally, there's a P0300 random misfire code. I would recommend addressing the O2 sensor issues first before considering any 'tune-up' work. Note: The term 'tune-up' is outdated and often used loosely in modern automotive service — it should be interpreted as specific repairs rather than a blanket recommendation.