Small signs are pointing to a new war for access to vehicle diagnostics.
When diagnosing misfires, it’s important to use tools that allow you to go beyond a simple code reader that displays a P03XX. Even an OEM-level scan tool can’t tell you what the firing voltage is or what the ignition pattern looks like. Nor can it tell you if the serial data is accurate or correct. For that kind of information you need a DVOM or a graphing multimeter/oscilloscope that can look at sensor voltages directly and display primary and secondary ignition patterns.
Section B, Item 8 of the ASE L1 certification task list states:
“Interpret OBD II scan tool data stream, diagnostic trouble codes (DTCs), freeze-frame data, system monitors, monitor readiness indicators, and trip and drive cycle information to determine system condition and verify repair effectiveness.” What ASE is talking about are the modes of OBD II scan tool protocol. Modes are usually denoted by a dollar sign and a two-digit number.
If your shop is not in California, the replacement of the catalytic converter is simple and typically there is only one replacement option. Most shops understand that they must replace the converter and that using a test pipe or bypassing the converter is bad for business and against the EPA regulations and could result in big fines.
Since the introduction of the OBD II system, manufacturers have continued to improve on the monitoring of evaporative emissions, with the complete evaporative system being under a scrutinized surveillance. Codes like P0440 to P0456 are all related to the fuel vapor control, including leaks.
Sensor replacement is critical to engine efficiency because a dirty MAF sensor will not respond as fast to air flow changes as a clean sensor.
The check engine light is on with a post catalyst fuel system lean code P2096, an oxygen (O2) sensor stuck lean B1/S2 code P2270, and an O2 sensor no activity B1/S2 code P0140.
This bulletin involves repositioning the upstream oxygen (O2) sensor connectors and replacing the wiring harness connector(s) and O2 sensor(s) as necessary.
If you confirm DTC P0420 (Catalyst System Efficiency Below Threshold) is stored in the ECM, determine if this bulletin applies by checking the ECM part number.
This real-world case study of a 2002 Chevy S-10 pickup, a 1995 Buick and a 1995 Lincoln Town Car illustrates why “chasing” trouble codes can get you lost in the Diagnostic Woods.
Nothing is more frustrating than diagnosing an intermittent cranking, no-start complaint with no diagnostic trouble codes (DTCs) and no apparent failure pattern. Much of the time, the cranking, no-start complaint lies with a failing crankshaft or camshaft position sensor. Many of these failures can be heat-related and might require several warm-up cycles to duplicate.
Generic OBD II tools may not give the complete picture of what is happening with a car. Consider what happened to me with my 2000 VW GTI 1.8T. The car had been intermittently stalling out over a period of a few weeks. The check engine light was not lit. One evening, as I was leaving work, the car stalled again. Fortunately, I had my laptop with me and had several diagnostic programs installed, so I ran a scan.