--- title: "RV Module Scan and Fault Trace: $285 an Hour, Credited" description: "Chassis and coach module scanning, voltage drop under load, parasitic draw logging and LP pressure while firing. $285 per hour in shop at Yorba Linda." focus_keyword: "rv module scan and fault trace rancho santa margarita" canonical: https://ocrv.me/services/inspection-and-estimating/in-depth-diagnostic-and-scan/ kind: subService updated: 2026-07-29 source: OCRV Center --- # In Depth Diagnostic and Scan: Buying Instrument Time > Codes point at circuits, not at parts. Diagnostic and scan time is **$285 per hour** with a one hour minimum, **credited in full** against an authorized repair. In shop only. ## What does an in depth diagnostic and scan session cover? An in depth diagnostic buys instrument time: module scanning, voltage drop under load, current logging and gas pressure while an appliance fires. OCRV Center performs it in shop in Yorba Linda for Rancho Santa Margarita owners at $285 per hour, one hour minimum, credited against an authorized repair. - A stored code names a circuit, not the component that failed in it - Intermittent faults need logging over time, so the unit stays here - Coach side multiplex systems are scanned as well as the chassis - The output is a measured finding, not a list of parts to try ### Key facts | Item | Value | | --- | --- | | Diagnostic rate | $285 per hour (One hour minimum, credited in full against an authorized repair) | | Price range | $285 to $2,500 (1 to 9 hours depending on how much logging the fault needs) | | Where it happens | In shop at the Yorba Linda facility (Scan tooling, load banks and instruments do not travel) | | Typical turnaround | 1 to 2 shop days (An intermittent fault logged overnight takes the second day) | | Systems scanned | Chassis over J1939 and J1708, plus Lippert OneControl, Firefly, Spyder and Precision Circuits | There is no mobile diagnostic option here and nothing about this session travels: the coach comes to the Yorba Linda floor, where the scan tooling, the load bank, the meters and a bay it can occupy overnight all live. An intermittent fault is found by watching a circuit for hours, and watching a circuit for hours is not something anybody does in a storage row. What you are buying is instrument time, billed at $285 per hour with a one hour minimum and credited in full against an authorized repair. Not a guess, not a parts swap, and not a code read off a handheld at a counter. The deliverable is a measured finding: this circuit drops one point four volts under a fourteen amp load, this module reports a switch that is open, this appliance sees nine inches of water column when it needs eleven. ## What you are actually buying by the hour There is no mobile diagnostic service on offer and no roadside alternative, because the tooling that makes this session worth paying for is bolted to a building. A stepped load bank for proving a generator. A recording logger that can sit on a circuit through the night. A four post lift so a harness can be followed along a chassis rail. A manometer, a thermal camera, and a bay the coach can occupy while a fault decides whether it feels like appearing. What the hour buys is measurement rather than opinion. Diagnosis on a modern coach is arithmetic performed with instruments: a circuit either drops more voltage than it should under a known load or it does not, an appliance either sees its specified gas pressure while firing or it does not, a battery bank either returns to its quiescent draw when the coach sleeps or something is awake. Every one of those is a number, and numbers are what stop a repair becoming a sequence of guesses. - Load bank time on a generator that fails only under real load - Overnight current logging for a bank that dies in storage - Voltage drop measurement across every segment of a suspect circuit - Manometer readings taken while two appliances draw together - Thermal survey of distribution panels and battery terminations ## A fault code names a circuit, not a part This is the most expensive misunderstanding in vehicle electrics and it costs owners real money. A stored code says a controller saw a value outside the range it expects on a given circuit. It does not say which element of that circuit produced the reading. The component at the end is one candidate. So are both connectors, the ground, the section of harness that runs past a heat source, and the controller itself. Buying the component is the most convenient of those options and rarely the correct one. So we read the code, save the freeze frame data, then test the circuit with a load in it. A high resistance joint reads perfectly on an open circuit meter and fails the instant current flows, which is exactly why owners who tested a wire at home concluded the wire was fine. It usually is fine. The crimp inside the connector on the end of it is not. > **warning:** Do not let anybody clear a code on an intermittent fault before it has been recorded with its freeze frame data. That record is often the only evidence of an event which may not repeat for two weeks. ## The coach side network most shops never scan Every modern coach carries two worlds. The chassis, which talks J1939 or J1708 on a diesel platform or a manufacturer protocol on a Ford F53, and which a truck shop can read. Then the coach side, where Lippert OneControl, Firefly Integrations G series boards, Spyder Controls and Precision Circuits panels run lighting, slides, awnings, tank levels, pumps and climate through multiplex modules and a control network. A shop with chassis tooling and nothing else reads half a coach and will tell you the other half is fine. That matters because multiplex changes what a symptom means. A dead light on a hardwired circuit is a bulb, a switch or a wire. A dead light on a multiplex system might be a module output, a network segment, a configuration file, or a wall switch reporting nothing at all to a controller that is working perfectly. Replacing the fixture on that system is a wasted afternoon, and we see it regularly on units that have been somewhere else first. ## How an intermittent fault gets caught rather than waited for The hardest faults are the ones that will not perform. A slide that failed twice in Bishop and has worked perfectly for six weeks. A bank that dies over a long weekend and holds fine on the shop floor for two days. Lights that quit once the coach reaches afternoon temperature. None of those can be diagnosed by observation, because the observation window is longer than anybody's patience. The answer is instrumentation and time. A recording logger goes on the suspect branch, sampling continuously, and the coach sits with its systems armed. Heat related faults get the unit parked in sun with thermocouples on the suspect junctions. Parasitic draw work runs through a full night, because most modules take between twenty minutes and four hours to actually go to sleep, and a spot reading taken at five in the afternoon proves nothing at all. That is the honest reason some sessions need a second day. ## Why there is a one hour minimum and what it usually resolves The minimum exists because setting up is most of the cost. Getting the coach into a bay, connecting tooling to two networks, exporting the data and reading the history takes the better part of an hour before any thinking happens. Charging for fifteen minutes of that would mean either doing it badly or absorbing it into somebody else's repair, and neither of those is honest. The good news is what a single hour covers. A fault that is repeatable on demand is very often resolved inside it: a ground stud, a corroded connector, a switch input, a gas pressure reading that explains three complaints at once. That hour bills at $285 and credits in full against an authorized repair, so an owner who proceeds with the fix has paid for the diagnosis once. Where the fault needs logging instead, we tell you before the hour is up rather than after the money is spent. ## The limits of a diagnostic session A session establishes what is wrong now, with numbers. It does not predict what will fail next and it does not survey the rest of the vehicle. If you want condition across every system rather than an answer to one fault, that is a different purchase and it is priced differently. We will say which one your question needs before taking money for either. It also does not always end with a part. A meaningful proportion of sessions conclude that the component the owner expected to be faulty is measuring correctly, and that the real finding is a connection, a supply pressure or a configuration. Those results feel unsatisfying and they are the most valuable ones, because they are the point at which somebody stops buying parts. The figures go in writing either way. ## Which vehicles we do this on Diesel pushers and luxury coaches carry the most networks and produce the most work, because a single ground fault can raise warnings on four systems at once. Super C units combine a medium duty chassis with a coach network built by a different company, and the boundary between the two is a common fault line. Sprinter builds pack everything into a small space with long earth returns. On the commercial side, tractors and fire apparatus arrive with multiplexed body controls where downtime is counted in shifts rather than days. ## Cost $285 to $2,500, based on 1 to 9 labor hours at $285 per hour. Written repair estimate is $150, credited in full against an authorized repair. All work is performed in shop. ## Questions and answers ### What does the one hour minimum on diagnostic time actually cover? Getting the unit into a bay, connecting tooling to the chassis and coach networks, exporting codes and freeze frame data, and reading the history. That setup is most of the cost. A repeatable fault is often solved inside the same hour, and the hour credits in full against an authorized repair. ### Why does a stored fault code not tell you which part has failed? Because it only reports that a controller saw a value outside its expected range on a circuit. The component, both connectors, the ground and the harness are all candidates. Connections fail more often than devices. We load the circuit and measure voltage drop, since a bad joint reads perfectly on an open circuit meter. ### How do you catch a fault that only shows up once a week? With a recording logger on the suspect branch and the unit left armed in a bay. Heat related faults get the coach parked in sun with thermocouples fitted. That is why some sessions run into a second day, and it is the only method that reliably catches something which will not perform on request. ### Do you scan coach side multiplex systems as well as the chassis? Yes, and it matters. Lippert OneControl, Firefly Integrations, Spyder Controls and Precision Circuits panels run lighting, slides, tank levels and climate through modules and a network. A chassis only scan reads half the coach. On a multiplex system a dead fixture is frequently a module output or a switch input instead. ### What is a parasitic draw test and why does it need a whole night? It measures what the unit keeps drawing after everything is switched off, using a clamp and a logger on the negative. Modules take anywhere from twenty minutes to four hours to actually sleep, so a spot reading taken in the afternoon proves nothing. Logging through the night shows which branch never settles. ### What happens if the session finds nothing wrong with the part I suspected? That is a common and useful outcome. You get the measurements showing the component is within specification, plus the finding that does explain the symptom, which is usually a connection, a ground, a supply pressure or a configuration. The billed hours still credit against any repair you authorize here afterwards. --- Source: [OCRV Center](https://ocrv.me/services/inspection-and-estimating/in-depth-diagnostic-and-scan/). Last verified 2026-07-29.