How to Resource Square
Resource Centre 3 min read

How to Diagnose intermittent failure to start engine.

Share Resource:
Diagnostics & Test Equipment OBD Diagnostic Vehicle Electronics & Engine Management How to Technicians 3 min read

Resource Highlights

In this article you will find a step by step guide on how to Diagnose intermittent failure to start engine.

The vehicle: Renault Laguna 1.8L Petrol

The symptoms: Intermittent failure to start engine.

The solution: The technician connected Delphi’s DS350E diagnostic tool to the OBD diagnostics socket to interrogate the vehicle’s fault code history.

Fault returned: ‘DF017 Flywheel signal sensor circuit, tooth signal missing – intermittent,’ indicating a fault with the crankshaft sensor. 

Step 2

The fault codes were erased using DS350E.

After erasing the fault, the technician restarted the engine several times to find the fault was still present, as confirmed by a second run of DS350E diagnostics. 

Step 3

The technician removed the crankshaft sensor and visually inspected the part for damage of measurement tip. 

Step 4

In preparation for further interrogation with Delphi’s PicoScope, the technician disconnected the crankshaft sensor from the harness and inserted a Delphi mini-bob (mini break-out box) between the two connections.

Delphi’s mini-bob connectors are used to enable technicians to gain access to the wiring without damaging the insulation. 

Step 5

The technician connected PicoScope to Delphi’s convertible PC, DS350E, (or other laptop computer) and started the PicoScope software. The technician then used the Delphi waveform library, choosing Delphi/Automotive/ Sensors/Crankshaft/Inductive/Running or Cranking.

This opened up a reference waveform, which demonstrated how a good sensor should perform. Opening up the library automatically enables the correct measurement settings for the PicoScope.

Step 6

The help guide automatically opened with information on how to connect the PicoScope, some example waveforms, and technical information (where applicable).

The technician followed the easy to understand instructions, exclusive to the Delphi PicoScope software, to insert the PicoScope probe into the two pin test lead adaptor, otherwise known as the mini-bob (already fitted to the sensor connection). 

Step 7

With the measurement settings already set and the probe connected to the mini-bob, the technician started the engine and began diagnostics by hitting the space bar to start capturing waveforms.

The technician found a good signal from the crankshaft sensor, with waveform patterns matching the example.

Step 8

The technician fitted a Delphi break-out box to the ECU to determine why it was still showing a fault.

The PicoScope was then connected to the correct pin numbers on the break-out box in order to once again capture a waveform from the crankshaft sensor. At this point it was found that there was no signal from the sensor to the ECU. 

Step 9

The wiring harness was visually inspected for signs of damage.

This led to the discovery of a soldered connection in the wiring harness from a previous modification. 

Step 10

The acupuncture probe was fitted to both sides of the soldered joint, with a direct connection to two channels on the PicoScope.

Once connected, the technician captured waveforms with the Delphi PicoScope software to find when the wiring harness was moved, the signal was lost on the ECU side of the soldered joint – indicating a broken wire.

Step 11

Using a harness repair kit, the technician repaired the broken wire and re-tested the signal using PicoScope and the ECU break-out box to establish there was now a good signal between the sensor and ECU.

Once this was confirmed, the technician disconnected the PicoScope, break-out box and mini-bob. 

Step 12

The final step was for the technician to re-interrogate with the DS350E, clear all fault codes to confirm that the fault has been eliminated.

Job done!

Technician’s Tool Box

DS350E

Delphi’s latest innovation in vehicle diagnostics, the DS350E convertible PC, offers advanced and up-to-date diagnostic software, providing capability across the vehicle’s key electronic systems.

PicoScope

Equipped with exclusive software, developed by Delphi engineers, the 4-channel scope kit provides technicians with the ability to interrogate the vehicle’s electronic and mechanical systems more effectively when identifying faulty components.

Harness Repair Kit

Electrical system harnesses, also known as wiring looms, are vital to system performance. Delphi’s harness repair kits enable technicians to repair the harness efficiently and cost-effectively.

Break-out Box

An interface between the vehicle’s ECU (or specific component depending on the type of break-out box used) and the wiring loom, Delphi’s break-out box facilitates the use of a multi-meter or PicoScope to measure voltage, continuity and waveforms. This tool provides a safe and effective way of testing wiring looms without puncturing the insulation with needle probes.

Mini-bob

Specifically designed to analyze the increasing number of sensors, actuators and electronic circuits, Delphi’s ‘mini-bob’ break-out cables allow the testing of sensors while avoiding damage to vehicle components. Delphi offers these cables across a wide range of vehicle electronics systems, including braking and air conditioning.

 

The specified form no longer exists or is currently unpublished.

Related article resources and products

    Part diagnostics fuel injection electronic test kit
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    Electronic Injector Test Kit

    With today’s Common Rail injector technology, it’s no longer sufficient to just measure resistance to check a coil’s health – you also need to measure inductance for an immediate and accurate assessment. Previously separate tools would have been needed for this. Not with our Electronic Injector Test kit. Otherwise known as the ‘buzz tool,’ or part number YDT720, you’ll be able to quickly test the electrical integrity of all makes of solenoid Common Rail injectors on vehicle. The simple,hand-held tool measures the injectors core criteria, allowing you to quickly compare values and identify if any are not within a comparable performance range, or confirm specific electronic failures which may indicate an unrepairable injector. You can also use it in conjunction with our solvent cleaning kit to resolve early-stage lacquering. All with just one tool, saving significant time and cost for the garage.
    pt-dte-pass-banner
    Diagnostics & Test Equipment

    Pass-Thru Diagnostics

    Our DS-Flash™ pass-thru package does what its name suggests – it allows garages to ‘pass-thru’ to vehicle manufacturer’s websites to access valuable repair and maintenance information. With DS-Flash you’ll be able to perform dealer-level diagnostics, download software updates, reprogram ECUs and access OE technical data and service schedule information, without the need for expensive dealer-only tools. The full kit is compliant with VM programming requirements and comes complete with a DS-Flash™ VCI, cables, a battery support unit and a laptop PC, pre-configured for key brands. Users will also benefit from our 12-month support package, which includes training and technical support for both the equipment, registration to the VM web portal and installation and use of the VM software. So from now on, jobs that were turned away, or referred back to the dealer network, can now be managed in house.
    Part diagnostics fuel injection hd3000 high pressure tool
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    HD3000 High Pressure Diagnostic Tool

    Designed for specialist workshops, our patented HD3000, part number YDT840, simplifies the diagnosis of faults with current and future-generation diesel and gasoline high pressure fuel systems, on all vehicle types. With one tool users will be able to safely set and electronically control any pressure testpoint , up to 3000 bar, in order to investigate the full range of pressures and analyse the performance of the fuel injection system – previously this level of flexibility, accuracy and pressure capability could only be achieved with a system-dedicated test bench. Containing an electronic control device, hydraulic block and electrical device, it incorporates multiple dedicated test routines, as well as an IMV cleaning procedure. All this can be achieved without changing any ECU parameter, dismantling the fuel injection system, or taking the vehicle out on a road test – helping workshops save valuable time and deliver faster service turnarounds.
    Part diagnostics fuel injection lo35 low pressure tool
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    LP35 Low Pressure Diagnostic Tool

    Designed for the garage technician, LP35, part number YDT810, is a highly precise, ultra-fast, affordable hand-held tester for the low-pressure side of light, medium and heavy duty vehicles. With a single tool, you can perform quick and accurate pressure analysis across a wide range of positive and negative pressures, from minus one through to positive 35 bar -that’s why we called it the LP35. Unlike other entry level equivalents, it’s also compatible with most low-pressure circuits, as well as different fluids, so you’ll no longer need separate negative and positive pressure tools, saving both time and money. Add to this its static and dynamic functionality, and you’ve got a highly versatile, highly capable low-pressure tool.
    Part diagnostics fuel injection hd3000 high pressure tool blueprint
    Diagnostics & Test Equipment

    Fuel Injection Diagnostics

    Due to the design of today’s advanced fuel injection technology, electronic diagnostic tools require additional support to accurately trace faulty components – the ECU diagnostic software  can often go no further than failure mode identification, which does not always pinpoint the particular part of the system that has failed and can result in the unnecessary replacement of complete systems. That’s where we come in. We know exactly what is required when diagnosing this technology – after all, the chances are we designed and manufactured it in the first place. So, we’ve developed a range of simple, low-cost, on-vehicle diesel diagnostic tools to help you and your customer save time and money.
    Part diagnostics fuel injection sealed rail kit
    Diagnostics & Test Equipment Fuel Injection Diagnostic

    Sealed Rail Diagnostic Kit

    Because Common Rail systems operate at extremely high pressures, any loss in pressure will have a knock-on effect on the vehicle – causing a progressive reduction in power and even a complete engine shut down. It is therefore imperative that any such issues are identified and resolved as early as possible. We have just the answer. Our Sealed Rail diagnostic kit, part number YDT850, provides simple, low-cost on-vehicle capability for all makes of Common Rail pumps and injectors. Consisting of a sealed rail pressure tester and injector back leakage measurement equipment, users can check the pressure being generated by a Common Rail pump and identify individual injectors that fail, meaning only faulty components will need to be replaced.
      where to buy

      Find out where to buy Delphi parts

      where to repair

      Find your nearest Service & Diesel Centres

      Select your Region