LM4 swap, no spark
LM4 swap, no spark Hi guys,
I'm swapping in an 04 LM4 from an Envoy into my 04 ZR2 Blazer.
Stock block, ls1 car intake, L59 injectors, and running the stock Blazer's P59 PCM with an LM7 cable throttle body and MAF.
Built the harness myself based on the stock Blazer harness, but populating the silverado wires and pins as needed.
I have segment swapped with HPTuners.
04 express van Engine and Engine diagnostics segment swapped in (for cable throttle and old style AC controls) but most parameters from the L59 dropped in over that.
So now the problem: I'm not getting any spark.
I've confirmed +12V and good ground at each coil subharness connector.
I've traced and confirmed with a multimeter each PCM pin to the connector.
VATS is removed.
hptuners is reading RPM signal when I crank, so CKP seems to be working.
Any thoughts on what to check?
I'm swapping in an 04 LM4 from an Envoy into my 04 ZR2 Blazer.
Stock block, ls1 car intake, L59 injectors, and running the stock Blazer's P59 PCM with an LM7 cable throttle body and MAF.
Built the harness myself based on the stock Blazer harness, but populating the silverado wires and pins as needed.
I have segment swapped with HPTuners.
04 express van Engine and Engine diagnostics segment swapped in (for cable throttle and old style AC controls) but most parameters from the L59 dropped in over that.
So now the problem: I'm not getting any spark.
I've confirmed +12V and good ground at each coil subharness connector.
I've traced and confirmed with a multimeter each PCM pin to the connector.
VATS is removed.
hptuners is reading RPM signal when I crank, so CKP seems to be working.
Any thoughts on what to check?
- all coil subharness connector to pcm pins
- 12V+ source at pink wires at coil subconnector harness
- ground (black) wires to ground at coil subconnector harness
- all 3 cam position sensor wires to each PCM pinout
I will reconfirm all PCM grounds and power tonight, but I checked this a week when I ran the wires so I would be surprised to see anything out of place.
Check the harness grounds at the harness/engine side. 2 at rear of intake. 1 maybe on side of block pass or driver side.
Are u sure your ign relay is staying hot while cranking? Needs hot with key on and start.
Are u sure your ign relay is staying hot while cranking? Needs hot with key on and start.
I will reconfirm the +12V is staying hot while cranking tonight, but I'm using the ENG1 fuse (upsized to 15A) on the stock UBEC (A9 & B9 pins on C2, circuit 239) which is supposed to stay hot during cranking.
