I have a '99 7.3 The problem I'm having is that I'm getting a code 1391 &1393.
This is the glow plug's left and right bank curcit low. All the plugs are good and I'm getting volts on the down side of the relay. Could a low volt reading give this code? When I key on I have 11.6V and when I go to start I have 10.9v
Also, is the fuel bowl heater element tyied in to this relay?
Thanks, John

 

A) your truck must be from california B) the glow plug module reads current to each bank of glow plugs if either bank or both draw less current than it should it will through a code. it does not mean all the GP's are bad it could only be one on each side. you need to test each GP...read up on this thread: https://www.ford-trucks.com/forums/4...ke-thread.html


on edit: here is soome more to the point info... http://download-v5.streamload.com/cb...d/Ford/gpr.pdf

 

I checked all the glow plugs and have .8 to 1.0 omh on all of them. The relay is working fine. I heard of the plug that goes on the valve cover may cause this, is that true? If not, any ideas would be helpful. Thanks lost

 

Your truck must be a California emissions vehicle to get a GP code, but a 1999 will not have a GPCM but a regular relay with a little metal shunt the GP wires attach to that allows the PCM to monitor them. A problem with this shunt or being missing or a short in the wire coming off the center post of the shunt can cause this. Or the Fusible links can.

Glow Plug Monitoring System for California OBD II and Excursion
The glow plug system is monitored when the glow plugs are commanded on for more than 35 seconds. EOT needs to be below 55°C (131°F) for F-Series or 30°C (86 °F) for Econoline and battery voltage must be between 11.5-14 volts.

You can monitor glow plug amperage using scan tool PIDs GPMR and GPML.

DTC P1395 or P1396 will set on the bank that is reading less than 39 amps. Loose fitting pins in the circuit connectors causing high resistance or high resistance glow plug(s) on that bank could be the cause. A shorted circuit or low-resistance glow plug(s) on the opposite bank could also be the cause. Each bank needs to draw more than 39 amps.

DTC P1391 or P1393 will set when the monitor indicates that all four glow plugs are not being powered on the bank. An open in the glow plug circuits, glow plug relay, glow plugs or monitoring circuit could be the possible causes.

Both DTCs P1391 and P1393 together will set when the monitor indicates that all eight glow plugs are not being powered. An open in all glow plug circuits, the glow plug relay, glow plugs, fusible links or all three monitoring circuits could be the possible causes. If KOEO On-Demand Self Test DTC P0380 is also set, a concern on the glow plug relay triggering circuit will cause all three DTCs to set.