Engine Malfunction only when in reverse.

[Riff Clichard]

Hello,

My MK2 Ford Focus displays the Engine Malfunction message only when I put it in reverse.  Had it scanned and these codes were returned:

P1910:00     ODDTCs     Reverse Lamp Control Circuit Open

P1910:FF     CMDTCs     Reverse Lamp Control Circuit Open

I've no idea where the fuse is, hoping that is just the fuse.  Not sure where this control circuit is located.

Thanks for your help.

[rd457]

The reverse light is fuse F141, which also incidentally covers electric mirrors. It's a 10 amp. It's located in the passenger fusebox; you'll see a group of six (two columns of three) about mid-way up the right hand side, F141 is the top right of these. (Going by the Haynes diagram).

[Riff Clichard]

Thank you very much Lyndon.  I'll check that out and let you know mate. Thanks again.

[Riff Clichard]

Hi Lyndon,

I checked that fuse but there is no voltage present on either side of the fuse.  I removed to check it physically and it looked intact.  I checked the other 5 fuses next to it and only one (138) was ok, the rest didnt have voltage on any side of their pins.

Any ideas?

Thanks

[rd457]

Was the engine on when you checked? F141 will only get voltage when the ignition is on. Your multimeter's continuity mode will help test the fuse is intact btw.

F138 is for 'engine management' and automatic transmission. The other four in that group of six are for main and dipped headlights, which presumably need a certain combination of ignition and light switch position conditions for voltage to be supplied through them.

If the fuse is not the problem, there's relay R41 found in the engine bay fusebox which needs to be working for the reverse light to function as well as a few other things (from a glance at the diagrams provided in the Haynes manual). The bulb itself of course is part of the circuit and may have blown. If none of those then you need to check the wires and their connectors, for instance looking for a corroded connector at the GEM (passenger fusebox) or loose/corroded pin connection in the light's plug, or a broken wire.

[Riff Clichard]

I checked again today with the engine on, but no voltage present on either side of fuse 141 and others next to it.

[rd457]

Did you check the headlight fuses (F139, F140, F142 and F143) with the engine on and lights switched on? (The first two are main beam and the other two dipped beam)? I wouldn't expect voltage on those unless the actual lights are on. Let's not get too distracted by those though, unless those lights are also not working.

As for the reverse light, the diagram given in the Haynes manual shows two circuits being involved.

• A circuit from the battery positive terminal, passing through fuse F11, then through the ignition switch (when on), going into the passenger fusebox, where via some splice/joint/connector it then heads back out to the engine fusebox, passing through the coil (activation) wire of relay R41, and then off into the GEM within the passenger fusebox, within which it must get connected back to the battery negative terminal to complete the circuit though this detail is hidden.
• A circuit from the battery positive terminal, through fuse F12 (which I forgot to list previously), through the switched part of relay R41, off to the passenger fusebox where it passes through F141, off through the 'reverse light switch' (presumably closed by moving the gearstick into reverse position), back to the passenger fusebox where it splits off in two directions, one leg into the GEM (presumably to let the GEM detect if the circuit is powered), and the other leg off through the reverse light bulb and then to chassis ground E5 (located in the luggage compartment) which is its connection back to the battery negative terminal (via the chassis).

Per the use of the relay, power flowing through that second circuit depends upon power flowing through the first.

Since you can turn on the engine we can safely assume that fuse F11 and the ignition are fine.

So the list of possibilities for the failure are as follows:

• Blown bulb
• Blown fuse F12
• Blown fuse F141
• Bad relay R41
• Bad 'reverse light switch' (again, presumably a mechanism built into the gear stick mechanism)
• Broken wire / bad wire connection
• Faulty GEM / passenger fusebox

The unknown detail about the negative return via the GEM makes it difficult to rule certain things out based upon your observations thus far (I'm just going off of the Haynes circuit diagram). I could check the actual behaviour with my car (same as yours), but that will have to wait until tomorrow, if I remember.

What you could do next from a simple practical perspective:

• Check fuse F12 (engine fusebox). You'll see 12V on both sides if it's good.
• Try to examine the bulb to see if you can tell if it's blown.
• Try swapping relay R41 with a matching one (from within the fusebox, I'm not expecting you to have a spare) and see if this makes any difference, if so then this confirms it's the relay.
• Try checking F141 again, this time with both the engine on and in reverse gear, just in case the GEM is not completing the first circuit unless reverse gear is selected. If still no voltage on either side of F141 then I expect that we could then at least rule out the bulb. Otherwise if you do then get voltage at F141 then this suggests that it's either the 'reverse light switch' (via a different wire?) or the bulb or their corresponding wires/connections.
• Examine the connectors at the fuseboxes and connectors for corrosion/water.
• Test the tightness of pin connections in connectors. (Get a sowing pin of similar size to the wiring pin and see if the grip is tight when put into the female part of the connector).

[alanfp]

I would check the fuses with a continuity tester, rather than checking to see if there's 12v each side of it.  You can do that regardless of whether the circuit is live or not.

[unofix]

9 hours ago, rd457 said:

So the list of possibilities for the failure are as follows:

An excellent fault finding write up Lyndon 👍

Anyone could be forgiven for thinking you're a professional at this fault finding game. With your detailed analysis it shouldn't take the OP too long to be able to track down the issue.

[rd457]

44 minutes ago, unofix said:

An excellent fault finding write up Lyndon 👍

Anyone could be forgiven for thinking you're a professional at this fault finding game. With your detailed analysis it shouldn't take the OP too long to be able to track down the issue.

Thanks, I've been watching a ton of youtube videos over the past year. Before that I couldn't even confidently point at an alternator. 😊

[KenM]

That just shows what owning a Ford forces you to learn.😂

[KenM]

That should also be an inspiration to others who often think cars are beyond them. Just take your time and think logically and gather as much information as you can there’s a lot out there if you look.

[rd457]

Just double checking what I wrote last night, I missed a fuse. F25 is a part of the first circuit, coming before R41, so that's another element to be checked.

[Riff Clichard]

Thanks for your suggestions.  I'll try to check and get back to you.  Might take a while though.

[Riff Clichard]

Hello again,

 

Sorry for the late reply, I don't have a lot of time to work on the car unfortunately.

Anyway, I wanted to ask you something.  I checked the bulb which is good, I checked fuse F12 and it it was good.   There's still no voltage on either side of fuse F141.  I got as far as R41.  I tried to locate this relay but I can't find it on any diagrams online and was wondering if you know where it is located or did you actually mean R14, perhaps?

Thanks a lot for your help

[Riff Clichard]

I also tested the electric windows switch connector and there's no power at any of the wires that connect to the switch.

[RL123]

Have you checked the plugs into the GEM/BCM fuse box. Look for corrosion and dampness. Some have suffered from this.

instrument clusters have been known to play up but I would expect ‘u’ codes in the OBD error codes.

[rd457]

11 hours ago, Riff Clichard said:

I got as far as R41.  I tried to locate this relay but I can't find it on any diagrams online and was wondering if you know where it is located or did you actually mean R14, perhaps?

Ah, so I'm working off of the diagrams given in the Haynes manual. It definitely says R41, that's not a mistake. (Not that the Haynes info is entirely free of mistakes, they've mistyped F140 as F40 in one place and confusingly they show R14 existing in both the engine and passenger fuse boxes at the same time which is wierd...).

Anyway, pulling the cover of the engine bay fusebox out of my Mk2.5 Focus, I can see the the layout matches the diagram in the Haynes manual, albeit it they miss a few relays on one side, and the fuses are all labelled the same, however for some reason the relays have completely different numbers. 🤨 So the relay that Haynes have labelled R41 corresponds to R8...

Documenting actual engine fusebox labels to Haynes':

• Actual => Haynes
• R1 => unlabelled
• R2 => R33
• R3 => R273
• R4 => unlabelled
• R5 => R69
• R6 => unlabelled
• R7 => R164
• R8 => R41
• R9 => R34
• R10 => R14
• R11 => R32
• R12 => not shown
• R13 => not shown
• R14 => not shown

Haynes also makes reference to an R13 ('power hold relay') but does not show which this in in the fusebox diagrams, similarly R22 for 'starter relay' appears nowhere on their fusebox diagrams, and same for R212 'glow plug relay' (yes, this appears for some reason in a petrol engine specific book...).

For the passenger fusebox:

• Actual => Haynes
• R19 => R14
• R15 => R5

WTH Haynes???

And of course whilst I was indoors with the engine bay fusebox cover it had to start raining, letting rain water into my fusebox 🙄.

[Riff Clichard]

On 2/22/2023 at 9:15 AM, RL123 said:

Have you checked the plugs into the GEM/BCM fuse box. Look for corrosion and dampness. Some have suffered from this.

instrument clusters have been known to play up but I would expect ‘u’ codes in the OBD error codes.

Thanks, I will definitely check the cable connectors in the passenger fusebox.  I've seen a couple of videos where the fusebox, also called a Body Control Module (BCM) was replaced due to various electrical faults.

[Riff Clichard]

On 2/22/2023 at 6:28 PM, rd457 said:

Ah, so I'm working off of the diagrams given in the Haynes manual. It definitely says R41, that's not a mistake. (Not that the Haynes info is entirely free of mistakes, they've mistyped F140 as F40 in one place and confusingly they show R14 existing in both the engine and passenger fuse boxes at the same time which is wierd...).

Anyway, pulling the cover of the engine bay fusebox out of my Mk2.5 Focus, I can see the the layout matches the diagram in the Haynes manual, albeit it they miss a few relays on one side, and the fuses are all labelled the same, however for some reason the relays have completely different numbers. 🤨 So the relay that Haynes have labelled R41 corresponds to R8...

Documenting actual engine fusebox labels to Haynes':

• Actual => Haynes
• R1 => unlabelled
• R2 => R33
• R3 => R273
• R4 => unlabelled
• R5 => R69
• R6 => unlabelled
• R7 => R164
• R8 => R41
• R9 => R34
• R10 => R14
• R11 => R32
• R12 => not shown
• R13 => not shown
• R14 => not shown

Haynes also makes reference to an R13 ('power hold relay') but does not show which this in in the fusebox diagrams, similarly R22 for 'starter relay' appears nowhere on their fusebox diagrams, and same for R212 'glow plug relay' (yes, this appears for some reason in a petrol engine specific book...).

For the passenger fusebox:

• Actual => Haynes
• R19 => R14
• R15 => R5

WTH Haynes???

And of course whilst I was indoors with the engine bay fusebox cover it had to start raining, letting rain water into my fusebox 🙄.

OK, that explains the R41, wth is Haynes doing?  I'm sure R8 was ok when I checked last time using my Chinese relay tester but I'll check again.  By any chance, does your Haynes mention fuse F63 and its location?  I got hold of a schematic of the electric windows circuit and it shows a fuse F63 which comes before the window switch but I can't find it to check it.  It shows it as being located in 'X28-I Fusebox/Relay Plate 1'.

 

Thanks a lot

 

[rd457]

7 hours ago, Riff Clichard said:

By any chance, does your Haynes mention fuse F63 and its location?

Unfortunately not, the Haynes info just tells me that fuses F1-F36 are in the engine bay fusebox and F100-F143 are in the passenger footwell fusebox, nothing about any F37-F99 fuses.

[Riff Clichard]

A word of advice.....don't trust 100% a test lamp.

I unplugged each fuse to check it with a multimeter and guess what?  Fuse F12 tested good with the test lamp but not with the multimeter???  I replaced F12 and threw my test lamp away because everything now works.  I'm so p'd off for wasting all this time, yours and mine.  Thanks very much for all of your advice, I really appreciate it.  Damn fuses. lol

Thanks

[rd457]

No worries, glad you finally fixed it. 🙃

[Riff Clichard]

Appreciate your help.